661907856 has 40 divisors (see below), whose sum is σ = 1716318720. Its totient is φ = 219811456.

The previous prime is 661907849. The next prime is 661907867. The reversal of 661907856 is 658709166.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12720 + ... + 38543.

It is an arithmetic number, because the mean of its divisors is an integer number (42907968).

Almost surely, 2^661907856 is an apocalyptic number.

It is an amenable number.

661907856 is an abundant number, since it is smaller than the sum of its proper divisors (1054410864).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661907856 is a wasteful number, since it uses less digits than its factorization.

661907856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51543 (or 51537 counting only the distinct ones).

The product of its (nonzero) digits is 544320, while the sum is 48.

The square root of 661907856 is about 25727.5699590925. The cubic root of 661907856 is about 871.4968971753.

The spelling of 661907856 in words is "six hundred sixty-one million, nine hundred seven thousand, eight hundred fifty-six".