20809900 has 18 divisors (see below), whose sum is σ = 45157700. Its totient is φ = 8323920.

The previous prime is 20809847. The next prime is 20809903. The reversal of 20809900 is 990802.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (20809903) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 103950 + ... + 104149.

Almost surely, 2^20809900 is an apocalyptic number.

20809900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20809900 is an abundant number, since it is smaller than the sum of its proper divisors (24347800).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20809900 is a wasteful number, since it uses less digits than its factorization.

20809900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 208113 (or 208106 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 20809900 is about 4561.7869305788. The cubic root of 20809900 is about 275.0573984872.

The spelling of 20809900 in words is "twenty million, eight hundred nine thousand, nine hundred".