208991969 has 2 divisors, whose sum is σ = 208991970. Its totient is φ = 208991968.

The previous prime is 208991953. The next prime is 208992037. The reversal of 208991969 is 969199802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 208947025 + 44944 = 14455^2 + 212^2 .

It is a cyclic number.

It is not a de Polignac number, because 208991969 - 2⁴ = 208991953 is a prime.

It is a super-2 number, since 2×208991969² = 87355286212993922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 208991969.

It is not a weakly prime, because it can be changed into another prime (208996969) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104495984 + 104495985.

It is an arithmetic number, because the mean of its divisors is an integer number (104495985).

Almost surely, 2^208991969 is an apocalyptic number.

It is an amenable number.

208991969 is a deficient number, since it is larger than the sum of its proper divisors (1).

208991969 is an equidigital number, since it uses as much as digits as its factorization.

208991969 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 629856, while the sum is 53.

The square root of 208991969 is about 14456.5545341897. The cubic root of 208991969 is about 593.4396127073.

The spelling of 208991969 in words is "two hundred eight million, nine hundred ninety-one thousand, nine hundred sixty-nine".