209864891 has 2 divisors, whose sum is σ = 209864892. Its totient is φ = 209864890.

The previous prime is 209864873. The next prime is 209864927. The reversal of 209864891 is 198468902.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 209864891 - 2¹⁸ = 209602747 is a prime.

It is not a weakly prime, because it can be changed into another prime (209864801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104932445 + 104932446.

It is an arithmetic number, because the mean of its divisors is an integer number (104932446).

Almost surely, 2^209864891 is an apocalyptic number.

209864891 is a deficient number, since it is larger than the sum of its proper divisors (1).

209864891 is an equidigital number, since it uses as much as digits as its factorization.

209864891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 248832, while the sum is 47.

The square root of 209864891 is about 14486.7142927580. The cubic root of 209864891 is about 594.2646953335.

The spelling of 209864891 in words is "two hundred nine million, eight hundred sixty-four thousand, eight hundred ninety-one".