21057756 has 24 divisors (see below), whose sum is σ = 49689360. Its totient is φ = 6940032.

The previous prime is 21057731. The next prime is 21057763. The reversal of 21057756 is 65775012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8791 + ... + 10926.

It is an arithmetic number, because the mean of its divisors is an integer number (2070390).

Almost surely, 2^21057756 is an apocalyptic number.

It is an amenable number.

21057756 is an abundant number, since it is smaller than the sum of its proper divisors (28631604).

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

21057756 is a wasteful number, since it uses less digits than its factorization.

21057756 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19813 (or 19811 counting only the distinct ones).

The product of its (nonzero) digits is 14700, while the sum is 33.

The square root of 21057756 is about 4588.8730642719. The cubic root of 21057756 is about 276.1451137756.

The spelling of 21057756 in words is "twenty-one million, fifty-seven thousand, seven hundred fifty-six".