209640961 has 2 divisors, whose sum is σ = 209640962. Its totient is φ = 209640960.

The previous prime is 209640943. The next prime is 209640967. The reversal of 209640961 is 169046902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 200760561 + 8880400 = 14169^2 + 2980^2 .

It is a cyclic number.

It is not a de Polignac number, because 209640961 - 2¹⁹ = 209116673 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 209640961.

It is not a weakly prime, because it can be changed into another prime (209640967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104820480 + 104820481.

It is an arithmetic number, because the mean of its divisors is an integer number (104820481).

Almost surely, 2^209640961 is an apocalyptic number.

It is an amenable number.

209640961 is a deficient number, since it is larger than the sum of its proper divisors (1).

209640961 is an equidigital number, since it uses as much as digits as its factorization.

209640961 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 37.

The square root of 209640961 is about 14478.9834242601. The cubic root of 209640961 is about 594.0532560413.

The spelling of 209640961 in words is "two hundred nine million, six hundred forty thousand, nine hundred sixty-one".