177

177 = 3 x 59.

177 is a digitally balanced number: In its binary representation (10110001), it has the same number of zeros as ones.

177 is the smallest possible magic constant for a 3 x 3 prime magic square.

177 is the number of graphs with seven edges.

Each internal angle of a regular 120-sided polygon is 177 degrees.

177 Irma is a fairly large, dark asteroid discovered in 1877.

Source: Number Gossip

15

15 = 3 x 5.

15 is a triangular number, the sum of the first five positive integers: 1 + 2 + 3 + 4 + 5 = 15.

7 can be partitioned in 15 ways.

A three-by-three magic square has the magic constant 15 (the sum of each row, column, or diagonal).

For n greater than 15, at least one number between n and 2n is the product of three different primes.

15 has a unique representation as a sum of four squares: 15 = 1² + 1² + 2² + 3².

15 is the smallest number that has three representations as a sum of three primes: 15 = 2 + 2 + 11= 3 + 5 + 7 = 5 + 5 + 5.


15 is the atomic number of the element phosphorus.

Source: Number Gossip

111

111 = 3 x 37.

111 is the smallest palindromic number such that the sum of its digits is one of its prime factors.

111 is a number that cannot be written as a sum of three squares.

A six-by-six magic square using the numbers 1 through 36 has a magic constant of 111.


111 would be the magic constant for the smallest magic square composed only of prime numbers if one were counted as a prime.


In J.R.R. Tolkien’s The Lord of the Rings, Bilbo Baggins disappears from his eleventy-first (111th) birthday party and from the Shire.

Sources: Number Gossip