18191818991 has 2 divisors, whose sum is σ = 18191818992. Its totient is φ = 18191818990.

The previous prime is 18191818961. The next prime is 18191818993. The reversal of 18191818991 is 19981819181.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18191818991 - 2¹⁰ = 18191817967 is a prime.

Together with 18191818993, 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 (18191818993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9095909495 + 9095909496.

It is an arithmetic number, because the mean of its divisors is an integer number (9095909496).

Almost surely, 2^18191818991 is an apocalyptic number.

18191818991 is a deficient number, since it is larger than the sum of its proper divisors (1).

18191818991 is an equidigital number, since it uses as much as digits as its factorization.

18191818991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 373248, while the sum is 56.

The spelling of 18191818991 in words is "eighteen billion, one hundred ninety-one million, eight hundred eighteen thousand, nine hundred ninety-one".