21815712 has 72 divisors (see below), whose sum is σ = 62506080. Its totient is φ = 7217280.

The previous prime is 21815683. The next prime is 21815737. The reversal of 21815712 is 21751812.

It is a tau number, because it is divible by the number of its divisors (72).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 60589 + ... + 60947.

It is an arithmetic number, because the mean of its divisors is an integer number (868140).

Almost surely, 2^21815712 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 21815712, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31253040).

21815712 is an abundant number, since it is smaller than the sum of its proper divisors (40690368).

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

21815712 is a wasteful number, since it uses less digits than its factorization.

21815712 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 586 (or 575 counting only the distinct ones).

The product of its digits is 1120, while the sum is 27.

The square root of 21815712 is about 4670.7292792454. The cubic root of 21815712 is about 279.4193408894.

The spelling of 21815712 in words is "twenty-one million, eight hundred fifteen thousand, seven hundred twelve".