20718851 has 2 divisors, whose sum is σ = 20718852. Its totient is φ = 20718850.

The previous prime is 20718839. The next prime is 20718857. The reversal of 20718851 is 15881702.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20718851 - 2¹⁸ = 20456707 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (20718857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10359425 + 10359426.

It is an arithmetic number, because the mean of its divisors is an integer number (10359426).

Almost surely, 2^20718851 is an apocalyptic number.

20718851 is a deficient number, since it is larger than the sum of its proper divisors (1).

20718851 is an equidigital number, since it uses as much as digits as its factorization.

20718851 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 20718851 is about 4551.7964585425. The cubic root of 20718851 is about 274.6556615821.

The spelling of 20718851 in words is "twenty million, seven hundred eighteen thousand, eight hundred fifty-one".