21642589 has 2 divisors, whose sum is σ = 21642590. Its totient is φ = 21642588.

The previous prime is 21642587. The next prime is 21642601. The reversal of 21642589 is 98524612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21576025 + 66564 = 4645^2 + 258^2 .

It is a cyclic number.

It is not a de Polignac number, because 21642589 - 2¹ = 21642587 is a prime.

Together with 21642587, 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 (21642587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10821294 + 10821295.

It is an arithmetic number, because the mean of its divisors is an integer number (10821295).

Almost surely, 2^21642589 is an apocalyptic number.

It is an amenable number.

21642589 is a deficient number, since it is larger than the sum of its proper divisors (1).

21642589 is an equidigital number, since it uses as much as digits as its factorization.

21642589 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34560, while the sum is 37.

The square root of 21642589 is about 4652.1596060324. The cubic root of 21642589 is about 278.6782474666.

It can be divided in two parts, 2164 and 2589, that added together give a triangular number (4753 = T₉₇).

The spelling of 21642589 in words is "twenty-one million, six hundred forty-two thousand, five hundred eighty-nine".