21752991 has 12 divisors (see below), whose sum is σ = 33838168. Its totient is φ = 13386384.

The previous prime is 21752971. The next prime is 21752999. The reversal of 21752991 is 19925712.

21752991 = 608² + 609² + ... + 661².

It is not a de Polignac number, because 21752991 - 2⁵ = 21752959 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21752999) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 92845 + ... + 93078.

Almost surely, 2^21752991 is an apocalyptic number.

21752991 is a deficient number, since it is larger than the sum of its proper divisors (12085177).

21752991 is a wasteful number, since it uses less digits than its factorization.

21752991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 185942 (or 185939 counting only the distinct ones).

The product of its digits is 11340, while the sum is 36.

The square root of 21752991 is about 4664.0101843800. The cubic root of 21752991 is about 279.1513034490.

The spelling of 21752991 in words is "twenty-one million, seven hundred fifty-two thousand, nine hundred ninety-one".