18506831621 has 2 divisors, whose sum is σ = 18506831622. Its totient is φ = 18506831620.

The previous prime is 18506831599. The next prime is 18506831677. The reversal of 18506831621 is 12613860581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17322508225 + 1184323396 = 131615^2 + 34414^2 .

It is a cyclic number.

It is not a de Polignac number, because 18506831621 - 2⁶ = 18506831557 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18506831221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9253415810 + 9253415811.

It is an arithmetic number, because the mean of its divisors is an integer number (9253415811).

Almost surely, 2^18506831621 is an apocalyptic number.

It is an amenable number.

18506831621 is a deficient number, since it is larger than the sum of its proper divisors (1).

18506831621 is an equidigital number, since it uses as much as digits as its factorization.

18506831621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 69120, while the sum is 41.

The spelling of 18506831621 in words is "eighteen billion, five hundred six million, eight hundred thirty-one thousand, six hundred twenty-one".