21387264 has 72 divisors (see below), whose sum is σ = 58001580. Its totient is φ = 7008256.

The previous prime is 21387257. The next prime is 21387277. The reversal of 21387264 is 46278312.

It is a super-2 number, since 2×21387264² = 914830122811392, which contains 22 as substring.

Its product of digits (16128) is a multiple of the sum of its prime divisors (64).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 362467 + ... + 362525.

Almost surely, 2^21387264 is an apocalyptic number.

21387264 is a gapful number since it is divisible by the number (24) 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 21387264, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29000790).

21387264 is an abundant number, since it is smaller than the sum of its proper divisors (36614316).

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

21387264 is an frugal number, since it uses more digits than its factorization.

21387264 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 143 (or 64 counting only the distinct ones).

The product of its digits is 16128, while the sum is 33.

The square root of 21387264 is about 4624.6366343746. The cubic root of 21387264 is about 277.5780220512.

The spelling of 21387264 in words is "twenty-one million, three hundred eighty-seven thousand, two hundred sixty-four".