21520756 has 12 divisors (see below), whose sum is σ = 38372292. Its totient is φ = 10557248.

The previous prime is 21520747. The next prime is 21520771. The reversal of 21520756 is 65702512.

It can be written as a sum of positive squares in 2 ways, for example, as 18576100 + 2944656 = 4310^2 + 1716^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50545 + ... + 50968.

It is an arithmetic number, because the mean of its divisors is an integer number (3197691).

Almost surely, 2^21520756 is an apocalyptic number.

It is an amenable number.

21520756 is a deficient number, since it is larger than the sum of its proper divisors (16851536).

21520756 is a wasteful number, since it uses less digits than its factorization.

21520756 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101570 (or 101568 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 28.

The square root of 21520756 is about 4639.0468848676. The cubic root of 21520756 is about 278.1543403967.

The spelling of 21520756 in words is "twenty-one million, five hundred twenty thousand, seven hundred fifty-six".