209899121 has 4 divisors (see below), whose sum is σ = 210777600. Its totient is φ = 209020644.

The previous prime is 209899117. The next prime is 209899199. The reversal of 209899121 is 121998902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 209899121 - 2² = 209899117 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (209899021) 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 in 3 ways as a sum of consecutive naturals, for example, 438881 + ... + 439358.

It is an arithmetic number, because the mean of its divisors is an integer number (52694400).

Almost surely, 2^209899121 is an apocalyptic number.

It is an amenable number.

209899121 is a deficient number, since it is larger than the sum of its proper divisors (878479).

209899121 is an equidigital number, since it uses as much as digits as its factorization.

209899121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 878478.

The product of its (nonzero) digits is 23328, while the sum is 41.

The square root of 209899121 is about 14487.8956719049. The cubic root of 209899121 is about 594.2970027458.

The spelling of 209899121 in words is "two hundred nine million, eight hundred ninety-nine thousand, one hundred twenty-one".