21390912 has 56 divisors (see below), whose sum is σ = 62890400. Its totient is φ = 7129728.

The previous prime is 21390911. The next prime is 21390977. The reversal of 21390912 is 21909312.

It is a super-2 number, since 2×21390912² = 915142232383488, which contains 22 as substring.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21390911) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4462 + ... + 7917.

Almost surely, 2^21390912 is an apocalyptic number.

It is an amenable number.

21390912 is an abundant number, since it is smaller than the sum of its proper divisors (41499488).

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

21390912 is a wasteful number, since it uses less digits than its factorization.

21390912 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12400 (or 12384 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 21390912 is about 4625.0310269230. The cubic root of 21390912 is about 277.5938032042.

Subtracting 21390912 from its reverse (21909312), we obtain a square (518400 = 720²).

It can be divided in two parts, 213 and 90912, that added together give a cube (91125 = 45³).

The spelling of 21390912 in words is "twenty-one million, three hundred ninety thousand, nine hundred twelve".