21039984 has 60 divisors (see below), whose sum is σ = 67297776. Its totient is φ = 6011136.

The previous prime is 21039971. The next prime is 21039989. The reversal of 21039984 is 48993012.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21039989) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9429 + ... + 11444.

Almost surely, 2^21039984 is an apocalyptic number.

21039984 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21039984 is an abundant number, since it is smaller than the sum of its proper divisors (46257792).

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

21039984 is a wasteful number, since it uses less digits than its factorization.

21039984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20894 (or 20885 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 21039984 is about 4586.9362323887. The cubic root of 21039984 is about 276.0674063466.

The spelling of 21039984 in words is "twenty-one million, thirty-nine thousand, nine hundred eighty-four".