21387238 has 4 divisors (see below), whose sum is σ = 32080860. Its totient is φ = 10693618.

The previous prime is 21387227. The next prime is 21387251. The reversal of 21387238 is 83278312.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5346808 + ... + 5346811.

It is an arithmetic number, because the mean of its divisors is an integer number (8020215).

Almost surely, 2^21387238 is an apocalyptic number.

21387238 is a deficient number, since it is larger than the sum of its proper divisors (10693622).

21387238 is a wasteful number, since it uses less digits than its factorization.

21387238 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10693621.

The product of its digits is 16128, while the sum is 34.

The square root of 21387238 is about 4624.6338233421. The cubic root of 21387238 is about 277.5779095694.

The spelling of 21387238 in words is "twenty-one million, three hundred eighty-seven thousand, two hundred thirty-eight".