191134221721 has 9 divisors (see below), whose sum is σ = 203046670749. Its totient is φ = 179884037184.

The previous prime is 191134221709. The next prime is 191134221727. The reversal of 191134221721 is 127122431191.

The square root of 191134221721 is 437189.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 28160531721 + 162973690000 = 167811^2 + 403700^2 .

It is not a de Polignac number, because 191134221721 - 2⁵ = 191134221689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (191134221727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 7419355 + ... + 7445071.

Almost surely, 2^191134221721 is an apocalyptic number.

191134221721 is the 437189-th square number.

191134221721 is the 218595-th centered octagonal number.

It is an amenable number.

191134221721 is a deficient number, since it is larger than the sum of its proper divisors (11912449028).

191134221721 is an frugal number, since it uses more digits than its factorization.

191134221721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51468 (or 25734 counting only the distinct ones).

The product of its digits is 6048, while the sum is 34.

The spelling of 191134221721 in words is "one hundred ninety-one billion, one hundred thirty-four million, two hundred twenty-one thousand, seven hundred twenty-one".