51531691 has 4 divisors (see below), whose sum is σ = 51840432. Its totient is φ = 51222952.

The previous prime is 51531679. The next prime is 51531731. The reversal of 51531691 is 19613515.

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

It is a cyclic number.

It is not a de Polignac number, because 51531691 - 2⁵ = 51531659 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51531631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 154120 + ... + 154453.

It is an arithmetic number, because the mean of its divisors is an integer number (12960108).

Almost surely, 2^51531691 is an apocalyptic number.

51531691 is a deficient number, since it is larger than the sum of its proper divisors (308741).

51531691 is a wasteful number, since it uses less digits than its factorization.

51531691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 308740.

The product of its digits is 4050, while the sum is 31.

The square root of 51531691 is about 7178.5577242229. The cubic root of 51531691 is about 372.1272423816.

The spelling of 51531691 in words is "fifty-one million, five hundred thirty-one thousand, six hundred ninety-one".