21815252 has 6 divisors (see below), whose sum is σ = 38176698. Its totient is φ = 10907624.

The previous prime is 21815251. The next prime is 21815257. The reversal of 21815252 is 25251812.

It can be written as a sum of positive squares in only one way, i.e., 11600836 + 10214416 = 3406^2 + 3196^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21815251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2726903 + ... + 2726910.

It is an arithmetic number, because the mean of its divisors is an integer number (6362783).

Almost surely, 2^21815252 is an apocalyptic number.

It is an amenable number.

21815252 is a deficient number, since it is larger than the sum of its proper divisors (16361446).

21815252 is a wasteful number, since it uses less digits than its factorization.

21815252 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5453817 (or 5453815 counting only the distinct ones).

The product of its digits is 1600, while the sum is 26.

The square root of 21815252 is about 4670.6800361403. The cubic root of 21815252 is about 279.4173769562.

The spelling of 21815252 in words is "twenty-one million, eight hundred fifteen thousand, two hundred fifty-two".