57

57 = 3 x 19.

57 is 111 in base 7.

57 is the sum of the 7th through 12th numbers: 7 + 8 + 9 + 10 + 11 + 12 = 57.

As a semiprime (a product of two primes), 57 is a Blum integer because its two prime factors, 3 and 19, are both Gaussian primes.

"57 Varieties" was the slogan of Pittsburgh's H. J. Heinz Company. In its early days, the company wanted to advertise the great number of choices of canned and bottled foods it offered for sale. Although the company had more than 60 products in 1892, the number 57 was chosen because the number "5" was Henry John Heinz's lucky number and the number "7" was his wife's lucky number.

Source: Wikipedia