21057536 has 52 divisors (see below), whose sum is σ = 43346772. Its totient is φ = 10223616.

The previous prime is 21057523. The next prime is 21057541. The reversal of 21057536 is 63575012.

It can be written as a sum of positive squares in 2 ways, for example, as 12390400 + 8667136 = 3520^2 + 2944^2 .

It is a zygodrome in base 4.

It is a junction number, because it is equal to n+sod(n) for n = 21057499 and 21057508.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 217040 + ... + 217136.

Almost surely, 2^21057536 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 21057536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21673386).

21057536 is an abundant number, since it is smaller than the sum of its proper divisors (22289236).

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

21057536 is an frugal number, since it uses more digits than its factorization.

21057536 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 174 (or 152 counting only the distinct ones).

The product of its (nonzero) digits is 6300, while the sum is 29.

The square root of 21057536 is about 4588.8490931823. The cubic root of 21057536 is about 276.1441521009.

The spelling of 21057536 in words is "twenty-one million, fifty-seven thousand, five hundred thirty-six".