20808947 has 4 divisors (see below), whose sum is σ = 21292920. Its totient is φ = 20324976.

The previous prime is 20808943. The next prime is 20808989. The reversal of 20808947 is 74980802.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20808947 - 2² = 20808943 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20808947.

It is not an unprimeable number, because it can be changed into a prime (20808943) 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, 241922 + ... + 242007.

It is an arithmetic number, because the mean of its divisors is an integer number (5323230).

Almost surely, 2^20808947 is an apocalyptic number.

20808947 is a deficient number, since it is larger than the sum of its proper divisors (483973).

20808947 is an equidigital number, since it uses as much as digits as its factorization.

20808947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 483972.

The product of its (nonzero) digits is 32256, while the sum is 38.

The square root of 20808947 is about 4561.6824747016. The cubic root of 20808947 is about 275.0531996251.

The spelling of 20808947 in words is "twenty million, eight hundred eight thousand, nine hundred forty-seven".