18117181421 has 2 divisors, whose sum is σ = 18117181422. Its totient is φ = 18117181420.

The previous prime is 18117181363. The next prime is 18117181463. The reversal of 18117181421 is 12418171181.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16741513321 + 1375668100 = 129389^2 + 37090^2 .

It is a cyclic number.

It is not a de Polignac number, because 18117181421 - 2³⁰ = 17043439597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18117181021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9058590710 + 9058590711.

It is an arithmetic number, because the mean of its divisors is an integer number (9058590711).

Almost surely, 2^18117181421 is an apocalyptic number.

It is an amenable number.

18117181421 is a deficient number, since it is larger than the sum of its proper divisors (1).

18117181421 is an equidigital number, since it uses as much as digits as its factorization.

18117181421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3584, while the sum is 35.

The spelling of 18117181421 in words is "eighteen billion, one hundred seventeen million, one hundred eighty-one thousand, four hundred twenty-one".