18981618856397 has 2 divisors, whose sum is σ = 18981618856398. Its totient is φ = 18981618856396.

The previous prime is 18981618856363. The next prime is 18981618856427. The reversal of 18981618856397 is 79365881618981.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14598734247241 + 4382884609156 = 3820829^2 + 2093534^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18981618856397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18981618856357) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9490809428198 + 9490809428199.

It is an arithmetic number, because the mean of its divisors is an integer number (9490809428199).

Almost surely, 2^{18981618856397} is an apocalyptic number.

It is an amenable number.

18981618856397 is a deficient number, since it is larger than the sum of its proper divisors (1).

18981618856397 is an equidigital number, since it uses as much as digits as its factorization.

18981618856397 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1254113280, while the sum is 80.

The spelling of 18981618856397 in words is "eighteen trillion, nine hundred eighty-one billion, six hundred eighteen million, eight hundred fifty-six thousand, three hundred ninety-seven".