21525989 has 2 divisors, whose sum is σ = 21525990. Its totient is φ = 21525988.

The previous prime is 21525979. The next prime is 21525991. The reversal of 21525989 is 98952512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15484225 + 6041764 = 3935^2 + 2458^2 .

It is a cyclic number.

It is not a de Polignac number, because 21525989 - 2⁸ = 21525733 is a prime.

Together with 21525991, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21525979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10762994 + 10762995.

It is an arithmetic number, because the mean of its divisors is an integer number (10762995).

Almost surely, 2^21525989 is an apocalyptic number.

It is an amenable number.

21525989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21525989 is an equidigital number, since it uses as much as digits as its factorization.

21525989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 64800, while the sum is 41.

The square root of 21525989 is about 4639.6108673034. The cubic root of 21525989 is about 278.1768839619.

The spelling of 21525989 in words is "twenty-one million, five hundred twenty-five thousand, nine hundred eighty-nine".