188391385261 has 2 divisors, whose sum is σ = 188391385262. Its totient is φ = 188391385260.

The previous prime is 188391385249. The next prime is 188391385279. The reversal of 188391385261 is 162583193881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 123890624361 + 64500760900 = 351981^2 + 253970^2 .

It is an emirp because it is prime and its reverse (162583193881) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-188391385261 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (188391382261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 94195692630 + 94195692631.

It is an arithmetic number, because the mean of its divisors is an integer number (94195692631).

Almost surely, 2^188391385261 is an apocalyptic number.

It is an amenable number.

188391385261 is a deficient number, since it is larger than the sum of its proper divisors (1).

188391385261 is an equidigital number, since it uses as much as digits as its factorization.

188391385261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2488320, while the sum is 55.

The spelling of 188391385261 in words is "one hundred eighty-eight billion, three hundred ninety-one million, three hundred eighty-five thousand, two hundred sixty-one".