51561999 has 12 divisors (see below), whose sum is σ = 75247536. Its totient is φ = 34019712.

The previous prime is 51561997. The next prime is 51562001. The reversal of 51561999 is 99916515.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (51561997) and next prime (51562001).

It is not a de Polignac number, because 51561999 - 2¹ = 51561997 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51561997) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 28659 + ... + 30404.

It is an arithmetic number, because the mean of its divisors is an integer number (6270628).

Almost surely, 2^51561999 is an apocalyptic number.

51561999 is a deficient number, since it is larger than the sum of its proper divisors (23685537).

51561999 is a wasteful number, since it uses less digits than its factorization.

51561999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59166 (or 59163 counting only the distinct ones).

The product of its digits is 109350, while the sum is 45.

The square root of 51561999 is about 7180.6684229255. The cubic root of 51561999 is about 372.2001827532.

The spelling of 51561999 in words is "fifty-one million, five hundred sixty-one thousand, nine hundred ninety-nine".