21387236 has 24 divisors (see below), whose sum is σ = 42430080. Its totient is φ = 9351072.

The previous prime is 21387227. The next prime is 21387251. The reversal of 21387236 is 63278312.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9836 + ... + 11811.

It is an arithmetic number, because the mean of its divisors is an integer number (1767920).

Almost surely, 2^21387236 is an apocalyptic number.

21387236 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21387236 is a deficient number, since it is larger than the sum of its proper divisors (21042844).

21387236 is a wasteful number, since it uses less digits than its factorization.

21387236 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21683 (or 21681 counting only the distinct ones).

The product of its digits is 12096, while the sum is 32.

The square root of 21387236 is about 4624.6336071088. The cubic root of 21387236 is about 277.5779009169.

The spelling of 21387236 in words is "twenty-one million, three hundred eighty-seven thousand, two hundred thirty-six".