661551656 has 32 divisors (see below), whose sum is σ = 1289088000. Its totient is φ = 317939520.

The previous prime is 661551647. The next prime is 661551679. The reversal of 661551656 is 656155166.

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, 28001 + ... + 45903.

It is an arithmetic number, because the mean of its divisors is an integer number (40284000).

Almost surely, 2^661551656 is an apocalyptic number.

It is an amenable number.

661551656 is a deficient number, since it is larger than the sum of its proper divisors (627536344).

661551656 is a wasteful number, since it uses less digits than its factorization.

661551656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18089 (or 18085 counting only the distinct ones).

The product of its digits is 162000, while the sum is 41.

The square root of 661551656 is about 25720.6464926526. The cubic root of 661551656 is about 871.3405396132.

The spelling of 661551656 in words is "six hundred sixty-one million, five hundred fifty-one thousand, six hundred fifty-six".