191288912921 has 2 divisors, whose sum is σ = 191288912922. Its totient is φ = 191288912920.

The previous prime is 191288912909. The next prime is 191288912939. The reversal of 191288912921 is 129219882191.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 163620250000 + 27668662921 = 404500^2 + 166339^2 .

It is an emirp because it is prime and its reverse (129219882191) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 191288912921 - 2¹⁴ = 191288896537 is a prime.

It is not a weakly prime, because it can be changed into another prime (191288917921) 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 as a sum of consecutive naturals, namely, 95644456460 + 95644456461.

It is an arithmetic number, because the mean of its divisors is an integer number (95644456461).

Almost surely, 2^191288912921 is an apocalyptic number.

It is an amenable number.

191288912921 is a deficient number, since it is larger than the sum of its proper divisors (1).

191288912921 is an equidigital number, since it uses as much as digits as its factorization.

191288912921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 373248, while the sum is 53.

The spelling of 191288912921 in words is "one hundred ninety-one billion, two hundred eighty-eight million, nine hundred twelve thousand, nine hundred twenty-one".