20953809 has 20 divisors (see below), whose sum is σ = 33144804. Its totient is φ = 13146624.

The previous prime is 20953717. The next prime is 20953811. The reversal of 20953809 is 90835902.

It can be written as a sum of positive squares in 2 ways, for example, as 17139600 + 3814209 = 4140^2 + 1953^2 .

It is not a de Polignac number, because 20953809 - 2⁸ = 20953553 is a prime.

It is a super-2 number, since 2×20953809² = 878124223216962, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (20953819) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 6232 + ... + 8985.

Almost surely, 2^20953809 is an apocalyptic number.

It is an amenable number.

20953809 is a deficient number, since it is larger than the sum of its proper divisors (12190995).

20953809 is a wasteful number, since it uses less digits than its factorization.

20953809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15246 (or 15237 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 20953809 is about 4577.5330692416. The cubic root of 20953809 is about 275.6899874525.

The spelling of 20953809 in words is "twenty million, nine hundred fifty-three thousand, eight hundred nine".