6440686631 has 4 divisors (see below), whose sum is σ = 6500880072. Its totient is φ = 6380493192.

The previous prime is 6440686621. The next prime is 6440686639. The reversal of 6440686631 is 1366860446.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6440686631 is a prime.

It is a super-2 number, since 2×6440686631² = 82964888557484260322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6440686639) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30096560 + ... + 30096773.

It is an arithmetic number, because the mean of its divisors is an integer number (1625220018).

Almost surely, 2^6440686631 is an apocalyptic number.

6440686631 is a deficient number, since it is larger than the sum of its proper divisors (60193441).

6440686631 is a wasteful number, since it uses less digits than its factorization.

6440686631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60193440.

The product of its (nonzero) digits is 497664, while the sum is 44.

The square root of 6440686631 is about 80253.8885724549. Note that the first 3 decimals coincide. The cubic root of 6440686631 is about 1860.5616131767.

The spelling of 6440686631 in words is "six billion, four hundred forty million, six hundred eighty-six thousand, six hundred thirty-one".