18685636391 has 2 divisors, whose sum is σ = 18685636392. Its totient is φ = 18685636390.

The previous prime is 18685636349. The next prime is 18685636423. The reversal of 18685636391 is 19363658681.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 18685636391 - 2²⁶ = 18618527527 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18685636331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9342818195 + 9342818196.

It is an arithmetic number, because the mean of its divisors is an integer number (9342818196).

Almost surely, 2^18685636391 is an apocalyptic number.

18685636391 is a deficient number, since it is larger than the sum of its proper divisors (1).

18685636391 is an equidigital number, since it uses as much as digits as its factorization.

18685636391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5598720, while the sum is 56.

The spelling of 18685636391 in words is "eighteen billion, six hundred eighty-five million, six hundred thirty-six thousand, three hundred ninety-one".