21720589 has 8 divisors (see below), whose sum is σ = 23892480. Its totient is φ = 19744780.

The previous prime is 21720583. The next prime is 21720599. The reversal of 21720589 is 98502712.

It is not a de Polignac number, because 21720589 - 2³ = 21720581 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720581) 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 in 7 ways as a sum of consecutive naturals, for example, 6829 + ... + 9490.

It is an arithmetic number, because the mean of its divisors is an integer number (2986560).

Almost surely, 2^21720589 is an apocalyptic number.

It is an amenable number.

21720589 is a deficient number, since it is larger than the sum of its proper divisors (2171891).

21720589 is an equidigital number, since it uses as much as digits as its factorization.

21720589 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16352 (or 16330 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 21720589 is about 4660.5352696874. The cubic root of 21720589 is about 279.0126320167.

The spelling of 21720589 in words is "twenty-one million, seven hundred twenty thousand, five hundred eighty-nine".