15661980 has 36 divisors (see below), whose sum is σ = 47508552. Its totient is φ = 4176480.

The previous prime is 15661973. The next prime is 15661991. The reversal of 15661980 is 8916651.

15661980 is a `hidden beast` number, since 1 + 566 + 1 + 98 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 43326 + ... + 43685.

It is an arithmetic number, because the mean of its divisors is an integer number (1319682).

Almost surely, 2^15661980 is an apocalyptic number.

15661980 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

15661980 is an abundant number, since it is smaller than the sum of its proper divisors (31846572).

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

15661980 is a wasteful number, since it uses less digits than its factorization.

15661980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87026 (or 87021 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 36.

The square root of 15661980 is about 3957.5219519290. The cubic root of 15661980 is about 250.1970712775.

It can be divided in two parts, 15661 and 980, that added together give a square (16641 = 129²).

The spelling of 15661980 in words is "fifteen million, six hundred sixty-one thousand, nine hundred eighty".