20918851 has 2 divisors, whose sum is σ = 20918852. Its totient is φ = 20918850.

The previous prime is 20918819. The next prime is 20918917. The reversal of 20918851 is 15881902.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20918851 - 2⁵ = 20918819 is a prime.

It is not a weakly prime, because it can be changed into another prime (20918951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10459425 + 10459426.

It is an arithmetic number, because the mean of its divisors is an integer number (10459426).

Almost surely, 2^20918851 is an apocalyptic number.

20918851 is a deficient number, since it is larger than the sum of its proper divisors (1).

20918851 is an equidigital number, since it uses as much as digits as its factorization.

20918851 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 20918851 is about 4573.7130430319. The cubic root of 20918851 is about 275.5365875763.

The spelling of 20918851 in words is "twenty million, nine hundred eighteen thousand, eight hundred fifty-one".