15561972 has 18 divisors (see below), whose sum is σ = 39337298. Its totient is φ = 5187312.

The previous prime is 15561971. The next prime is 15561983. The reversal of 15561972 is 27916551.

15561972 is a `hidden beast` number, since 1 + 5 + 561 + 97 + 2 = 666.

It can be written as a sum of positive squares in only one way, i.e., 14107536 + 1454436 = 3756^2 + 1206^2 .

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

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 432277 = 15561972 / (1 + 5 + 5 + 6 + 1 + 9 + 7 + 2).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15561971) 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, 216103 + ... + 216174.

Almost surely, 2^15561972 is an apocalyptic number.

15561972 is a gapful number since it is divisible by the number (12) formed by its first and last digit.

It is an amenable number.

15561972 is an abundant number, since it is smaller than the sum of its proper divisors (23775326).

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

15561972 is a wasteful number, since it uses less digits than its factorization.

15561972 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 432287 (or 432282 counting only the distinct ones).

The product of its digits is 18900, while the sum is 36.

The square root of 15561972 is about 3944.8665376664. The cubic root of 15561972 is about 249.6633976655.

The spelling of 15561972 in words is "fifteen million, five hundred sixty-one thousand, nine hundred seventy-two".