51686991 has 20 divisors (see below), whose sum is σ = 77908512. Its totient is φ = 34147008.

The previous prime is 51686977. The next prime is 51687023. The reversal of 51686991 is 19968615.

It is not a de Polignac number, because 51686991 - 2⁵ = 51686959 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51686191) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 6330 + ... + 11976.

Almost surely, 2^51686991 is an apocalyptic number.

51686991 is a deficient number, since it is larger than the sum of its proper divisors (26221521).

51686991 is a wasteful number, since it uses less digits than its factorization.

51686991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5772 (or 5763 counting only the distinct ones).

The product of its digits is 116640, while the sum is 45.

The square root of 51686991 is about 7189.3665228586. The cubic root of 51686991 is about 372.5006915592.

The spelling of 51686991 in words is "fifty-one million, six hundred eighty-six thousand, nine hundred ninety-one".