21312912 has 80 divisors (see below), whose sum is σ = 58121280. Its totient is φ = 6720000.

The previous prime is 21312911. The next prime is 21312913. The reversal of 21312912 is 21921312.

It is an interprime number because it is at equal distance from previous prime (21312911) and next prime (21312913).

It is not an unprimeable number, because it can be changed into a prime (21312911) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 84787 + ... + 85037.

It is an arithmetic number, because the mean of its divisors is an integer number (726516).

Almost surely, 2^21312912 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21312912, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29060640).

21312912 is an abundant number, since it is smaller than the sum of its proper divisors (36808368).

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

21312912 is a wasteful number, since it uses less digits than its factorization.

21312912 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 352 (or 346 counting only the distinct ones).

The product of its digits is 216, while the sum is 21.

The square root of 21312912 is about 4616.5909500409. The cubic root of 21312912 is about 277.2559854770.

Subtracting 21312912 from its reverse (21921312), we obtain a square (608400 = 780²).

The spelling of 21312912 in words is "twenty-one million, three hundred twelve thousand, nine hundred twelve".