191020009 has 2 divisors, whose sum is σ = 191020010. Its totient is φ = 191020008.

The previous prime is 191020001. The next prime is 191020073. The reversal of 191020009 is 900020191.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 174979984 + 16040025 = 13228^2 + 4005^2 .

It is a cyclic number.

It is not a de Polignac number, because 191020009 - 2³ = 191020001 is a prime.

It is not a weakly prime, because it can be changed into another prime (191020001) 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, 95510004 + 95510005.

It is an arithmetic number, because the mean of its divisors is an integer number (95510005).

Almost surely, 2^191020009 is an apocalyptic number.

It is an amenable number.

191020009 is a deficient number, since it is larger than the sum of its proper divisors (1).

191020009 is an equidigital number, since it uses as much as digits as its factorization.

191020009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 162, while the sum is 22.

The square root of 191020009 is about 13820.9988423413. The cubic root of 191020009 is about 575.9166314928.

The spelling of 191020009 in words is "one hundred ninety-one million, twenty thousand, nine".