21897984 has 36 divisors (see below), whose sum is σ = 58282616. Its totient is φ = 7299072.

The previous prime is 21897949. The next prime is 21898007. The reversal of 21897984 is 48979812.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13489 + ... + 15024.

Almost surely, 2^21897984 is an apocalyptic number.

21897984 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21897984 is an abundant number, since it is smaller than the sum of its proper divisors (36384632).

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

21897984 is an equidigital number, since it uses as much as digits as its factorization.

21897984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28532 (or 28518 counting only the distinct ones).

The product of its digits is 290304, while the sum is 48.

The square root of 21897984 is about 4679.5281813448. The cubic root of 21897984 is about 279.7701515079.

The spelling of 21897984 in words is "twenty-one million, eight hundred ninety-seven thousand, nine hundred eighty-four".