20809864 has 32 divisors (see below), whose sum is σ = 41616000. Its totient is φ = 9726912.

The previous prime is 20809847. The next prime is 20809903. The reversal of 20809864 is 46890802.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11142 + ... + 12874.

It is an arithmetic number, because the mean of its divisors is an integer number (1300500).

Almost surely, 2^20809864 is an apocalyptic number.

It is an amenable number.

20809864 is a deficient number, since it is larger than the sum of its proper divisors (20806136).

20809864 is a wasteful number, since it uses less digits than its factorization.

20809864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1837 (or 1833 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 37.

The square root of 20809864 is about 4561.7829847550. The cubic root of 20809864 is about 275.0572398756.

The spelling of 20809864 in words is "twenty million, eight hundred nine thousand, eight hundred sixty-four".