661872392172 has 18 divisors (see below), whose sum is σ = 1673066324748. Its totient is φ = 220624130712.

The previous prime is 661872392143. The next prime is 661872392177. The reversal of 661872392172 is 271293278166.

It is a happy number.

661872392172 is a `hidden beast` number, since 6 + 6 + 1 + 87 + 2 + 392 + 172 = 666.

It is a tau number, because it is divible by the number of its divisors (18).

It is not an unprimeable number, because it can be changed into a prime (661872392177) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9192672078 + ... + 9192672149.

Almost surely, 2^661872392172 is an apocalyptic number.

It is an amenable number.

661872392172 is an abundant number, since it is smaller than the sum of its proper divisors (1011193932576).

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

661872392172 is a wasteful number, since it uses less digits than its factorization.

661872392172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18385344237 (or 18385344232 counting only the distinct ones).

The product of its digits is 3048192, while the sum is 54.

The spelling of 661872392172 in words is "six hundred sixty-one billion, eight hundred seventy-two million, three hundred ninety-two thousand, one hundred seventy-two".