20718857 has 2 divisors, whose sum is σ = 20718858. Its totient is φ = 20718856.

The previous prime is 20718851. The next prime is 20718871. The reversal of 20718857 is 75881702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16491721 + 4227136 = 4061^2 + 2056^2 .

It is a cyclic number.

It is not a de Polignac number, because 20718857 - 2¹² = 20714761 is a prime.

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 20718857.

It is not a weakly prime, because it can be changed into another prime (20718851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10359428 + 10359429.

It is an arithmetic number, because the mean of its divisors is an integer number (10359429).

Almost surely, 2^20718857 is an apocalyptic number.

It is an amenable number.

20718857 is a deficient number, since it is larger than the sum of its proper divisors (1).

20718857 is an equidigital number, since it uses as much as digits as its factorization.

20718857 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31360, while the sum is 38.

The square root of 20718857 is about 4551.7971176229. The cubic root of 20718857 is about 274.6556880948.

The spelling of 20718857 in words is "twenty million, seven hundred eighteen thousand, eight hundred fifty-seven".