18991979072657 has 2 divisors, whose sum is σ = 18991979072658. Its totient is φ = 18991979072656.

The previous prime is 18991979072609. The next prime is 18991979072663. The reversal of 18991979072657 is 75627097919981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16916431735681 + 2075547336976 = 4112959^2 + 1440676^2 .

It is a cyclic number.

It is not a de Polignac number, because 18991979072657 - 2³⁸ = 18717101165713 is a prime.

It is not a weakly prime, because it can be changed into another prime (18991979074657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9495989536328 + 9495989536329.

It is an arithmetic number, because the mean of its divisors is an integer number (9495989536329).

Almost surely, 2^{18991979072657} is an apocalyptic number.

It is an amenable number.

18991979072657 is a deficient number, since it is larger than the sum of its proper divisors (1).

18991979072657 is an equidigital number, since it uses as much as digits as its factorization.

18991979072657 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1080203040, while the sum is 80.

The spelling of 18991979072657 in words is "eighteen trillion, nine hundred ninety-one billion, nine hundred seventy-nine million, seventy-two thousand, six hundred fifty-seven".