209931089 has 2 divisors, whose sum is σ = 209931090. Its totient is φ = 209931088.

The previous prime is 209931083. The next prime is 209931091. The reversal of 209931089 is 980139902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 208947025 + 984064 = 14455^2 + 992^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-209931089 is a prime.

Together with 209931091, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (209931083) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104965544 + 104965545.

It is an arithmetic number, because the mean of its divisors is an integer number (104965545).

Almost surely, 2^209931089 is an apocalyptic number.

It is an amenable number.

209931089 is a deficient number, since it is larger than the sum of its proper divisors (1).

209931089 is an equidigital number, since it uses as much as digits as its factorization.

209931089 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34992, while the sum is 41.

The square root of 209931089 is about 14488.9988957139. The cubic root of 209931089 is about 594.3271720355.

The spelling of 209931089 in words is "two hundred nine million, nine hundred thirty-one thousand, eighty-nine".