191998691 has 2 divisors, whose sum is σ = 191998692. Its totient is φ = 191998690.

The previous prime is 191998669. The next prime is 191998711. The reversal of 191998691 is 196899191.

It is a strong prime.

It is an emirp because it is prime and its reverse (196899191) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 169866161 and 161668961.

It is a cyclic number.

It is not a de Polignac number, because 191998691 - 2⁶ = 191998627 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (191998601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95999345 + 95999346.

It is an arithmetic number, because the mean of its divisors is an integer number (95999346).

Almost surely, 2^191998691 is an apocalyptic number.

191998691 is a deficient number, since it is larger than the sum of its proper divisors (1).

191998691 is an equidigital number, since it uses as much as digits as its factorization.

191998691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 314928, while the sum is 53.

The square root of 191998691 is about 13856.3592260016. The cubic root of 191998691 is about 576.8985170751.

The spelling of 191998691 in words is "one hundred ninety-one million, nine hundred ninety-eight thousand, six hundred ninety-one".