21987360 has 72 divisors (see below), whose sum is σ = 75036780. Its totient is φ = 5862912.

The previous prime is 21987331. The next prime is 21987373. The reversal of 21987360 is 6378912.

21987360 is a `hidden beast` number, since 219 + 87 + 360 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 21790224 + 197136 = 4668^2 + 444^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a nialpdrome in base 12.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6195 + ... + 9074.

Almost surely, 2^21987360 is an apocalyptic number.

21987360 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21987360 is an abundant number, since it is smaller than the sum of its proper divisors (53049420).

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

21987360 is a wasteful number, since it uses less digits than its factorization.

21987360 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15290 (or 15279 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21987360 is about 4689.0681377007. The cubic root of 21987360 is about 280.1502594862.

The spelling of 21987360 in words is "twenty-one million, nine hundred eighty-seven thousand, three hundred sixty".