661857680 has 40 divisors (see below), whose sum is σ = 1678713984. Its totient is φ = 240675200.

The previous prime is 661857671. The next prime is 661857697. The reversal of 661857680 is 86758166.

It is a tau number, because it is divible by the number of its divisors (40).

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, 375176 + ... + 376935.

Almost surely, 2^661857680 is an apocalyptic number.

It is an amenable number.

661857680 is an abundant number, since it is smaller than the sum of its proper divisors (1016856304).

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

661857680 is a wasteful number, since it uses less digits than its factorization.

661857680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 752135 (or 752129 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 47.

The square root of 661857680 is about 25726.5947999342. The cubic root of 661857680 is about 871.4748753118.

The spelling of 661857680 in words is "six hundred sixty-one million, eight hundred fifty-seven thousand, six hundred eighty".