661635956 has 12 divisors (see below), whose sum is σ = 1158064992. Its totient is φ = 330760248.

The previous prime is 661635943. The next prime is 661635991. The reversal of 661635956 is 659536166.

It is a self number, because there is not a number n which added to its sum of digits gives 661635956.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21041 + ... + 42023.

It is an arithmetic number, because the mean of its divisors is an integer number (96505416).

Almost surely, 2^661635956 is an apocalyptic number.

It is an amenable number.

661635956 is a deficient number, since it is larger than the sum of its proper divisors (496429036).

661635956 is a wasteful number, since it uses less digits than its factorization.

661635956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28870 (or 28868 counting only the distinct ones).

The product of its digits is 874800, while the sum is 47.

The square root of 661635956 is about 25722.2852017468. The cubic root of 661635956 is about 871.3775490123.

The spelling of 661635956 in words is "six hundred sixty-one million, six hundred thirty-five thousand, nine hundred fifty-six".