21987023520 has 384 divisors, whose sum is σ = 86582587392. Its totient is φ = 4556390400.

The previous prime is 21987023501. The next prime is 21987023521. The reversal of 21987023520 is 2532078912.

It is not an unprimeable number, because it can be changed into a prime (21987023521) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 21325405 + ... + 21326435.

It is an arithmetic number, because the mean of its divisors is an integer number (225475488).

Almost surely, 2^21987023520 is an apocalyptic number.

21987023520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21987023520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43291293696).

21987023520 is an abundant number, since it is smaller than the sum of its proper divisors (64595563872).

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

21987023520 is a wasteful number, since it uses less digits than its factorization.

21987023520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1644 (or 1636 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 39.

The spelling of 21987023520 in words is "twenty-one billion, nine hundred eighty-seven million, twenty-three thousand, five hundred twenty".