191651891 has 2 divisors, whose sum is σ = 191651892. Its totient is φ = 191651890.

The previous prime is 191651861. The next prime is 191651909. The reversal of 191651891 is 198156191.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (198156191) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 191651891 - 2¹⁰ = 191650867 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (191651851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95825945 + 95825946.

It is an arithmetic number, because the mean of its divisors is an integer number (95825946).

Almost surely, 2^191651891 is an apocalyptic number.

191651891 is a deficient number, since it is larger than the sum of its proper divisors (1).

191651891 is an equidigital number, since it uses as much as digits as its factorization.

191651891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19440, while the sum is 41.

The square root of 191651891 is about 13843.8394602076. The cubic root of 191651891 is about 576.5509643836.

The spelling of 191651891 in words is "one hundred ninety-one million, six hundred fifty-one thousand, eight hundred ninety-one".