18775711991 has 2 divisors, whose sum is σ = 18775711992. Its totient is φ = 18775711990.

The previous prime is 18775711967. The next prime is 18775711993. The reversal of 18775711991 is 19911757781.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18775711991 - 2²⁶ = 18708603127 is a prime.

Together with 18775711993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18775711993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9387855995 + 9387855996.

It is an arithmetic number, because the mean of its divisors is an integer number (9387855996).

Almost surely, 2^18775711991 is an apocalyptic number.

18775711991 is a deficient number, since it is larger than the sum of its proper divisors (1).

18775711991 is an equidigital number, since it uses as much as digits as its factorization.

18775711991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1111320, while the sum is 56.

The spelling of 18775711991 in words is "eighteen billion, seven hundred seventy-five million, seven hundred eleven thousand, nine hundred ninety-one".