20664989 has 4 divisors (see below), whose sum is σ = 21752640. Its totient is φ = 19577340.

The previous prime is 20664967. The next prime is 20665009. The reversal of 20664989 is 98946602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20664989 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 (20664929) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 543797 + ... + 543834.

It is an arithmetic number, because the mean of its divisors is an integer number (5438160).

Almost surely, 2^20664989 is an apocalyptic number.

It is an amenable number.

20664989 is a deficient number, since it is larger than the sum of its proper divisors (1087651).

20664989 is a wasteful number, since it uses less digits than its factorization.

20664989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1087650.

The product of its (nonzero) digits is 186624, while the sum is 44.

The square root of 20664989 is about 4545.8760431846. The cubic root of 20664989 is about 274.4174511209.

The spelling of 20664989 in words is "twenty million, six hundred sixty-four thousand, nine hundred eighty-nine".