21251764 has 12 divisors (see below), whose sum is σ = 38196004. Its totient is φ = 10338624.

The previous prime is 21251731. The next prime is 21251773. The reversal of 21251764 is 46715212.

It can be written as a sum of positive squares in 2 ways, for example, as 8363664 + 12888100 = 2892^2 + 3590^2 .

It is a super-2 number, since 2×21251764² = 903274946223392, which contains 22 as substring.

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, 71649 + ... + 71944.

Almost surely, 2^21251764 is an apocalyptic number.

It is an amenable number.

21251764 is a deficient number, since it is larger than the sum of its proper divisors (16944240).

21251764 is a wasteful number, since it uses less digits than its factorization.

21251764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143634 (or 143632 counting only the distinct ones).

The product of its digits is 3360, while the sum is 28.

The square root of 21251764 is about 4609.9635573397. The cubic root of 21251764 is about 276.9905769058.

Adding to 21251764 its reverse (46715212), we get a palindrome (67966976).

The spelling of 21251764 in words is "twenty-one million, two hundred fifty-one thousand, seven hundred sixty-four".