991218157977599 has 2 divisors, whose sum is σ = 991218157977600. Its totient is φ = 991218157977598.

The previous prime is 991218157977547. The next prime is 991218157977611. The reversal of 991218157977599 is 995779751812199.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991218157977599 - 2⁸ = 991218157977343 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991218157977499) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495609078988799 + 495609078988800.

It is an arithmetic number, because the mean of its divisors is an integer number (495609078988800).

Almost surely, 2^{991218157977599} is an apocalyptic number.

991218157977599 is a deficient number, since it is larger than the sum of its proper divisors (1).

991218157977599 is an equidigital number, since it uses as much as digits as its factorization.

991218157977599 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8101522800, while the sum is 89.

The spelling of 991218157977599 in words is "nine hundred ninety-one trillion, two hundred eighteen billion, one hundred fifty-seven million, nine hundred seventy-seven thousand, five hundred ninety-nine".