20812931 has 2 divisors, whose sum is σ = 20812932. Its totient is φ = 20812930.

The previous prime is 20812921. The next prime is 20812933. The reversal of 20812931 is 13921802.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20812931 - 2¹⁰ = 20811907 is a prime.

It is a super-2 number, since 2×20812931² = 866356193621522, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 20812933, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20812931.

It is not a weakly prime, because it can be changed into another prime (20812933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10406465 + 10406466.

It is an arithmetic number, because the mean of its divisors is an integer number (10406466).

Almost surely, 2^20812931 is an apocalyptic number.

20812931 is a deficient number, since it is larger than the sum of its proper divisors (1).

20812931 is an equidigital number, since it uses as much as digits as its factorization.

20812931 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 20812931 is about 4562.1191347881. The cubic root of 20812931 is about 275.0707520433.

The spelling of 20812931 in words is "twenty million, eight hundred twelve thousand, nine hundred thirty-one".