51531665 has 4 divisors (see below), whose sum is σ = 61838004. Its totient is φ = 41225328.

The previous prime is 51531659. The next prime is 51531679. The reversal of 51531665 is 56613515.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 28912129 + 22619536 = 5377^2 + 4756^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51531665 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5153162 + ... + 5153171.

It is an arithmetic number, because the mean of its divisors is an integer number (15459501).

Almost surely, 2^51531665 is an apocalyptic number.

It is an amenable number.

51531665 is a deficient number, since it is larger than the sum of its proper divisors (10306339).

51531665 is a wasteful number, since it uses less digits than its factorization.

51531665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10306338.

The product of its digits is 13500, while the sum is 32.

The square root of 51531665 is about 7178.5559132739. Note that the first 3 decimals coincide. The cubic root of 51531665 is about 372.1271797967.

The spelling of 51531665 in words is "fifty-one million, five hundred thirty-one thousand, six hundred sixty-five".