191920409 has 2 divisors, whose sum is σ = 191920410. Its totient is φ = 191920408.

The previous prime is 191920403. The next prime is 191920439. The reversal of 191920409 is 904029191.

191920409 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 176491225 + 15429184 = 13285^2 + 3928^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-191920409 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (191920403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95960204 + 95960205.

It is an arithmetic number, because the mean of its divisors is an integer number (95960205).

Almost surely, 2^191920409 is an apocalyptic number.

It is an amenable number.

191920409 is a deficient number, since it is larger than the sum of its proper divisors (1).

191920409 is an equidigital number, since it uses as much as digits as its factorization.

191920409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 35.

The square root of 191920409 is about 13853.5341700232. The cubic root of 191920409 is about 576.8201017683.

The spelling of 191920409 in words is "one hundred ninety-one million, nine hundred twenty thousand, four hundred nine".