18445795721 has 2 divisors, whose sum is σ = 18445795722. Its totient is φ = 18445795720.

The previous prime is 18445795717. The next prime is 18445795807. The reversal of 18445795721 is 12759754481.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12907459321 + 5538336400 = 113611^2 + 74420^2 .

It is a cyclic number.

It is not a de Polignac number, because 18445795721 - 2² = 18445795717 is a prime.

It is not a weakly prime, because it can be changed into another prime (18445794721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9222897860 + 9222897861.

It is an arithmetic number, because the mean of its divisors is an integer number (9222897861).

Almost surely, 2^18445795721 is an apocalyptic number.

It is an amenable number.

18445795721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18445795721 is an equidigital number, since it uses as much as digits as its factorization.

18445795721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2822400, while the sum is 53.

The spelling of 18445795721 in words is "eighteen billion, four hundred forty-five million, seven hundred ninety-five thousand, seven hundred twenty-one".