18978064639 has 2 divisors, whose sum is σ = 18978064640. Its totient is φ = 18978064638.

The previous prime is 18978064607. The next prime is 18978064657. The reversal of 18978064639 is 93646087981.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18978064639 - 2⁵ = 18978064607 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18978064439) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9489032319 + 9489032320.

It is an arithmetic number, because the mean of its divisors is an integer number (9489032320).

Almost surely, 2^18978064639 is an apocalyptic number.

18978064639 is a deficient number, since it is larger than the sum of its proper divisors (1).

18978064639 is an equidigital number, since it uses as much as digits as its factorization.

18978064639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15676416, while the sum is 61.

The spelling of 18978064639 in words is "eighteen billion, nine hundred seventy-eight million, sixty-four thousand, six hundred thirty-nine".