18520671991 has 2 divisors, whose sum is σ = 18520671992. Its totient is φ = 18520671990.

The previous prime is 18520671941. The next prime is 18520672057. The reversal of 18520671991 is 19917602581.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 18520671991 - 2⁹ = 18520671479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18520671931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9260335995 + 9260335996.

It is an arithmetic number, because the mean of its divisors is an integer number (9260335996).

Almost surely, 2^18520671991 is an apocalyptic number.

18520671991 is a deficient number, since it is larger than the sum of its proper divisors (1).

18520671991 is an equidigital number, since it uses as much as digits as its factorization.

18520671991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 272160, while the sum is 49.

The spelling of 18520671991 in words is "eighteen billion, five hundred twenty million, six hundred seventy-one thousand, nine hundred ninety-one".