209749409 has 2 divisors, whose sum is σ = 209749410. Its totient is φ = 209749408.

The previous prime is 209749387. The next prime is 209749429. The reversal of 209749409 is 904947902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 189750625 + 19998784 = 13775^2 + 4472^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-209749409 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 209749409.

It is not a weakly prime, because it can be changed into another prime (209749429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104874704 + 104874705.

It is an arithmetic number, because the mean of its divisors is an integer number (104874705).

Almost surely, 2^209749409 is an apocalyptic number.

It is an amenable number.

209749409 is a deficient number, since it is larger than the sum of its proper divisors (1).

209749409 is an equidigital number, since it uses as much as digits as its factorization.

209749409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 163296, while the sum is 44.

The square root of 209749409 is about 14482.7279543600. The cubic root of 209749409 is about 594.1556736564.

The spelling of 209749409 in words is "two hundred nine million, seven hundred forty-nine thousand, four hundred nine".