21057224 has 8 divisors (see below), whose sum is σ = 39482310. Its totient is φ = 10528608.

The previous prime is 21057209. The next prime is 21057241. The reversal of 21057224 is 42275012.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20994724 + 62500 = 4582^2 + 250^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21057224.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1316069 + ... + 1316084.

Almost surely, 2^21057224 is an apocalyptic number.

It is an amenable number.

21057224 is a deficient number, since it is larger than the sum of its proper divisors (18425086).

21057224 is a wasteful number, since it uses less digits than its factorization.

21057224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2632159 (or 2632155 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21057224 is about 4588.8150976042. The cubic root of 21057224 is about 276.1427882597.

The spelling of 21057224 in words is "twenty-one million, fifty-seven thousand, two hundred twenty-four".