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#math trivia for #April16: #107 is the square root of 11449. Is there another number whose square has the form aabbc? — Burt Kaliski Jr. (@modulomathy) April 17, 2012 Assuming that a is non-zero, the square root must be a three-digit number.  Let xyz be the digits of a number N, so that N = … Continue reading →

#math trivia for #April15:#106 is the smallest three-digit number that’s twice a prime.What’s the largest one? — Burt Kaliski Jr. (@modulomathy) April 15, 2012 The largest three-digit number that’s twice a prime is equal to two times the largest prime less than 500, which is 499.  The answer is 998.

#math trivia for #April14: #105 sets a new record for number of odd divisors. What is it and when will it be broken again? — Burt Kaliski Jr. (@modulomathy) April 14, 2012 There are eight odd divisors of 105:  1, 3, 5, 7, 15, 21, 35 and 105.  The total of eight makes sense given … Continue reading →

#math trivia for #April13: Second #FridayThe13th this year. Is there a third?What’s the most a year can have? The fewest? — Burt Kaliski Jr. (@modulomathy) April 13, 2012 This one is related to the answer to #92. The starting days of the month, as noted in that answer, have the following modular values (relative to January 1) … Continue reading →

#math trivia for #April12:#103 and 263 are primes that sum to 366.How many other ways can 366 be expressed as the sum of two primes? — Burt Kaliski Jr. (@modulomathy) April 12, 2012 There are 17 other ways (determined with the help of a spreadsheet): 7 359 13 353 17 349 19 347 29 337 … Continue reading →

#math trivia for #April11:  #102 contains three consecutive digits.  How many other numbers 100-366 have this property? — Burt Kaliski Jr. (@modulomathy) April 12, 2012 The simplest way is probably to look at the eight different possible sets of digits involved: 0,1,2:  102, 120, 201, 210 (4 ways) 1,2,3:  123, 132, 213, 231, 312, 321 … Continue reading →

Burt Kaliski Jr. (@modulomathy) 4/10/12 7:49 PM #math trivia for #April10: #101 is one of six day-numbers this year whose digits sum to 2. What are the others? What’s the most common sum? The other day-numbers with a digit-sum of 2 are 2, 11, 20, 110, and 200. The most common digit-sum is 10, which … Continue reading →

Burt Kaliski Jr. (@modulomathy) 4/9/12 8:19 AM #math trivia for #April9: In _signed decimal_, digits have values from -10 to +9. What’s another way to represent #100 in this notation? The usual way to represent 100 is with unsigned digits: 100 = 1*10^2 + 0*10^1 + 0*10^0 Another way to represent 100 is with signed … Continue reading →

Burt Kaliski Jr. (@modulomathy) 4/8/12 9:32 PM #math trivia for #April8: #99 is the last two-digit number this year. How many digits do the 366 days this year have overall? Overall, the 366 day-numbers this year have 990 digits: — 9 days have one digit — 9 total — 90 have two — 180 more … Continue reading →

Burt Kaliski Jr. (@modulomathy) 4/7/12 11:55 AM #math trivia for #April7: #98 is the product of a number and its double. What’s the number, and what product near 10000 has this property? The number is 7: 7*14 = 98. Consider the equation 2x^2 = 98. The product near 10000 with this property is 71*142 = … Continue reading →