18188221081 has 2 divisors, whose sum is σ = 18188221082. Its totient is φ = 18188221080.

The previous prime is 18188221061. The next prime is 18188221111. The reversal of 18188221081 is 18012288181.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12557219481 + 5631001600 = 112059^2 + 75040^2 .

It is a cyclic number.

It is not a de Polignac number, because 18188221081 - 2²⁹ = 17651350169 is a prime.

It is a super-2 number, since 2×18188221081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18188221021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9094110540 + 9094110541.

It is an arithmetic number, because the mean of its divisors is an integer number (9094110541).

Almost surely, 2^18188221081 is an apocalyptic number.

It is an amenable number.

18188221081 is a deficient number, since it is larger than the sum of its proper divisors (1).

18188221081 is an equidigital number, since it uses as much as digits as its factorization.

18188221081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16384, while the sum is 40.

The spelling of 18188221081 in words is "eighteen billion, one hundred eighty-eight million, two hundred twenty-one thousand, eighty-one".