21387402 has 28 divisors (see below), whose sum is σ = 48102930. Its totient is φ = 7128648.

The previous prime is 21387391. The next prime is 21387403. The reversal of 21387402 is 20478312.

It can be written as a sum of positive squares in only one way, i.e., 17065161 + 4322241 = 4131^2 + 2079^2 .

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 (21387403) by changing a digit.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 5877 + ... + 8792.

Almost surely, 2^21387402 is an apocalyptic number.

21387402 is an abundant number, since it is smaller than the sum of its proper divisors (26715528).

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

21387402 is an equidigital number, since it uses as much as digits as its factorization.

21387402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14689 (or 14674 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21387402 is about 4624.6515544417. The cubic root of 21387402 is about 277.5786190682.

The spelling of 21387402 in words is "twenty-one million, three hundred eighty-seven thousand, four hundred two".