191999971 has 2 divisors, whose sum is σ = 191999972. Its totient is φ = 191999970.

The previous prime is 191999963. The next prime is 191999987. The reversal of 191999971 is 179999191.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 191999971 - 2³ = 191999963 is a prime.

It is not a weakly prime, because it can be changed into another prime (191939971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95999985 + 95999986.

It is an arithmetic number, because the mean of its divisors is an integer number (95999986).

Almost surely, 2^191999971 is an apocalyptic number.

191999971 is a deficient number, since it is larger than the sum of its proper divisors (1).

191999971 is an equidigital number, since it uses as much as digits as its factorization.

191999971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 413343, while the sum is 55.

The square root of 191999971 is about 13856.4054141036. The cubic root of 191999971 is about 576.8997990777.

The spelling of 191999971 in words is "one hundred ninety-one million, nine hundred ninety-nine thousand, nine hundred seventy-one".