209931091 has 2 divisors, whose sum is σ = 209931092. Its totient is φ = 209931090.

The previous prime is 209931089. The next prime is 209931131. The reversal of 209931091 is 190139902.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 209931091 - 2¹ = 209931089 is a prime.

Together with 209931089, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (209931041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104965545 + 104965546.

It is an arithmetic number, because the mean of its divisors is an integer number (104965546).

Almost surely, 2^209931091 is an apocalyptic number.

209931091 is a deficient number, since it is larger than the sum of its proper divisors (1).

209931091 is an equidigital number, since it uses as much as digits as its factorization.

209931091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4374, while the sum is 34.

The square root of 209931091 is about 14488.9989647318. The cubic root of 209931091 is about 594.3271739229.

The spelling of 209931091 in words is "two hundred nine million, nine hundred thirty-one thousand, ninety-one".