191688221138 has 18 divisors (see below), whose sum is σ = 305457693093. Its totient is φ = 90201268320.

The previous prime is 191688221099. The next prime is 191688221317. The reversal of 191688221138 is 831122886191.

It can be written as a sum of positive squares in 2 ways, for example, as 175437835609 + 16250385529 = 418853^2 + 127477^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=309587.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 10516853 + ... + 10535063.

Almost surely, 2^191688221138 is an apocalyptic number.

191688221138 is a deficient number, since it is larger than the sum of its proper divisors (113769471955).

191688221138 is an frugal number, since it uses more digits than its factorization.

191688221138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36458 (or 18230 counting only the distinct ones).

The product of its digits is 331776, while the sum is 50.

Multiplying 191688221138 by its sum of digits (50), we get a square (9584411056900 = 3095870²).

The spelling of 191688221138 in words is "one hundred ninety-one billion, six hundred eighty-eight million, two hundred twenty-one thousand, one hundred thirty-eight".