191891761 has 2 divisors, whose sum is σ = 191891762. Its totient is φ = 191891760.

The previous prime is 191891719. The next prime is 191891797. The reversal of 191891761 is 167198191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 177023025 + 14868736 = 13305^2 + 3856^2 .

It is a cyclic number.

It is not a de Polignac number, because 191891761 - 2⁷ = 191891633 is a prime.

It is a super-2 number, since 2×191891761² = 73644895879362242, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (191891561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95945880 + 95945881.

It is an arithmetic number, because the mean of its divisors is an integer number (95945881).

Almost surely, 2^191891761 is an apocalyptic number.

It is an amenable number.

191891761 is a deficient number, since it is larger than the sum of its proper divisors (1).

191891761 is an equidigital number, since it uses as much as digits as its factorization.

191891761 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27216, while the sum is 43.

The square root of 191891761 is about 13852.5001714492. The cubic root of 191891761 is about 576.7913996539.

The spelling of 191891761 in words is "one hundred ninety-one million, eight hundred ninety-one thousand, seven hundred sixty-one".