21572521 has 2 divisors, whose sum is σ = 21572522. Its totient is φ = 21572520.

The previous prime is 21572513. The next prime is 21572527. The reversal of 21572521 is 12527512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12355225 + 9217296 = 3515^2 + 3036^2 .

It is a cyclic number.

It is not a de Polignac number, because 21572521 - 2³ = 21572513 is a prime.

It is not a weakly prime, because it can be changed into another prime (21572527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10786260 + 10786261.

It is an arithmetic number, because the mean of its divisors is an integer number (10786261).

Almost surely, 2^21572521 is an apocalyptic number.

It is an amenable number.

21572521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21572521 is an equidigital number, since it uses as much as digits as its factorization.

21572521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1400, while the sum is 25.

The square root of 21572521 is about 4644.6228049218. The cubic root of 21572521 is about 278.3771815493.

The spelling of 21572521 in words is "twenty-one million, five hundred seventy-two thousand, five hundred twenty-one".