191990999 has 2 divisors, whose sum is σ = 191991000. Its totient is φ = 191990998.

The previous prime is 191990993. The next prime is 191991043. The reversal of 191990999 is 999099191.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 191990999 - 2¹⁶ = 191925463 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191990993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95995499 + 95995500.

It is an arithmetic number, because the mean of its divisors is an integer number (95995500).

Almost surely, 2^191990999 is an apocalyptic number.

191990999 is a deficient number, since it is larger than the sum of its proper divisors (1).

191990999 is an equidigital number, since it uses as much as digits as its factorization.

191990999 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 531441, while the sum is 56.

The square root of 191990999 is about 13856.0816611335. The cubic root of 191990999 is about 576.8908129207.

The spelling of 191990999 in words is "one hundred ninety-one million, nine hundred ninety thousand, nine hundred ninety-nine".