18031795721 has 2 divisors, whose sum is σ = 18031795722. Its totient is φ = 18031795720.

The previous prime is 18031795679. The next prime is 18031795729. The reversal of 18031795721 is 12759713081.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16968709696 + 1063086025 = 130264^2 + 32605^2 .

It is an emirp because it is prime and its reverse (12759713081) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18031795721 is a prime.

It is not a weakly prime, because it can be changed into another prime (18031795729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9015897860 + 9015897861.

It is an arithmetic number, because the mean of its divisors is an integer number (9015897861).

Almost surely, 2^18031795721 is an apocalyptic number.

It is an amenable number.

18031795721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18031795721 is an equidigital number, since it uses as much as digits as its factorization.

18031795721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 105840, while the sum is 44.

The spelling of 18031795721 in words is "eighteen billion, thirty-one million, seven hundred ninety-five thousand, seven hundred twenty-one".