209401921 has 2 divisors, whose sum is σ = 209401922. Its totient is φ = 209401920.

The previous prime is 209401909. The next prime is 209401943. The reversal of 209401921 is 129104902.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 108680625 + 100721296 = 10425^2 + 10036^2 .

It is a cyclic number.

It is not a de Polignac number, because 209401921 - 2¹⁷ = 209270849 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 209401921.

It is not a weakly prime, because it can be changed into another prime (209401961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104700960 + 104700961.

It is an arithmetic number, because the mean of its divisors is an integer number (104700961).

Almost surely, 2^209401921 is an apocalyptic number.

It is an amenable number.

209401921 is a deficient number, since it is larger than the sum of its proper divisors (1).

209401921 is an equidigital number, since it uses as much as digits as its factorization.

209401921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 209401921 is about 14470.7263466628. The cubic root of 209401921 is about 593.8273833620.

The spelling of 209401921 in words is "two hundred nine million, four hundred one thousand, nine hundred twenty-one".