21312738 has 24 divisors (see below), whose sum is σ = 47771100. Its totient is φ = 6859104.

The previous prime is 21312727. The next prime is 21312751. The reversal of 21312738 is 83721312.

It can be written as a sum of positive squares in 2 ways, for example, as 18378369 + 2934369 = 4287^2 + 1713^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19893 + ... + 20936.

Almost surely, 2^21312738 is an apocalyptic number.

21312738 is an abundant number, since it is smaller than the sum of its proper divisors (26458362).

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

21312738 is a wasteful number, since it uses less digits than its factorization.

21312738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40866 (or 40863 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21312738 is about 4616.5721049281. The cubic root of 21312738 is about 277.2552309630.

The spelling of 21312738 in words is "twenty-one million, three hundred twelve thousand, seven hundred thirty-eight".