18619161721 has 2 divisors, whose sum is σ = 18619161722. Its totient is φ = 18619161720.

The previous prime is 18619161713. The next prime is 18619161763. The reversal of 18619161721 is 12716191681.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11371023225 + 7248138496 = 106635^2 + 85136^2 .

It is a cyclic number.

It is not a de Polignac number, because 18619161721 - 2³ = 18619161713 is a prime.

It is not a weakly prime, because it can be changed into another prime (18619161791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9309580860 + 9309580861.

It is an arithmetic number, because the mean of its divisors is an integer number (9309580861).

Almost surely, 2^18619161721 is an apocalyptic number.

It is an amenable number.

18619161721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18619161721 is an equidigital number, since it uses as much as digits as its factorization.

18619161721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 43.

The spelling of 18619161721 in words is "eighteen billion, six hundred nineteen million, one hundred sixty-one thousand, seven hundred twenty-one".