21087984 has 40 divisors (see below), whose sum is σ = 54652752. Its totient is φ = 7006720.

The previous prime is 21087971. The next prime is 21087991. The reversal of 21087984 is 48978012.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21652 + ... + 22604.

Almost surely, 2^21087984 is an apocalyptic number.

21087984 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21087984 is an abundant number, since it is smaller than the sum of its proper divisors (33564768).

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

21087984 is a wasteful number, since it uses less digits than its factorization.

21087984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1425 (or 1419 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 21087984 is about 4592.1655022440. The cubic root of 21087984 is about 276.2771842511.

The spelling of 21087984 in words is "twenty-one million, eighty-seven thousand, nine hundred eighty-four".