18451891961 has 2 divisors, whose sum is σ = 18451891962. Its totient is φ = 18451891960.

The previous prime is 18451891943. The next prime is 18451891967. The reversal of 18451891961 is 16919815481.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15492531961 + 2959360000 = 124469^2 + 54400^2 .

It is an emirp because it is prime and its reverse (16919815481) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18451891961 is a prime.

It is not a weakly prime, because it can be changed into another prime (18451891967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9225945980 + 9225945981.

It is an arithmetic number, because the mean of its divisors is an integer number (9225945981).

Almost surely, 2^18451891961 is an apocalyptic number.

It is an amenable number.

18451891961 is a deficient number, since it is larger than the sum of its proper divisors (1).

18451891961 is an equidigital number, since it uses as much as digits as its factorization.

18451891961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 622080, while the sum is 53.

The spelling of 18451891961 in words is "eighteen billion, four hundred fifty-one million, eight hundred ninety-one thousand, nine hundred sixty-one".