21312756 has 36 divisors (see below), whose sum is σ = 56711200. Its totient is φ = 6730128.

The previous prime is 21312751. The next prime is 21312763. The reversal of 21312756 is 65721312.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312751) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14896 + ... + 16263.

Almost surely, 2^21312756 is an apocalyptic number.

It is an amenable number.

21312756 is an abundant number, since it is smaller than the sum of its proper divisors (35398444).

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

21312756 is a wasteful number, since it uses less digits than its factorization.

21312756 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31188 (or 31183 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 21312756 is about 4616.5740544261. The cubic root of 21312756 is about 277.2553090163.

The spelling of 21312756 in words is "twenty-one million, three hundred twelve thousand, seven hundred fifty-six".