21620989 has 16 divisors (see below), whose sum is σ = 24498432. Its totient is φ = 18931968.

The previous prime is 21620953. The next prime is 21620999. The reversal of 21620989 is 98902612.

It is a cyclic number.

It is not a de Polignac number, because 21620989 - 2¹⁵ = 21588221 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 (21620999) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49717 + ... + 50149.

It is an arithmetic number, because the mean of its divisors is an integer number (1531152).

Almost surely, 2^21620989 is an apocalyptic number.

It is an amenable number.

21620989 is a deficient number, since it is larger than the sum of its proper divisors (2877443).

21620989 is a wasteful number, since it uses less digits than its factorization.

21620989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 636.

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 21620989 is about 4649.8375240432. The cubic root of 21620989 is about 278.5855066552.

The spelling of 21620989 in words is "twenty-one million, six hundred twenty thousand, nine hundred eighty-nine".