209804121 has 8 divisors (see below), whose sum is σ = 310820960. Its totient is φ = 139869396.

The previous prime is 209804083. The next prime is 209804131. The reversal of 209804121 is 121408902.

It is not a de Polignac number, because 209804121 - 2⁶ = 209804057 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 7770523 = 209804121 / (2 + 0 + 9 + 8 + 0 + 4 + 1 + 2 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209804131) 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 7 ways as a sum of consecutive naturals, for example, 3885235 + ... + 3885288.

It is an arithmetic number, because the mean of its divisors is an integer number (38852620).

Almost surely, 2^209804121 is an apocalyptic number.

It is an amenable number.

209804121 is a deficient number, since it is larger than the sum of its proper divisors (101016839).

209804121 is an equidigital number, since it uses as much as digits as its factorization.

209804121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7770532 (or 7770526 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 209804121 is about 14484.6167018668. The cubic root of 209804121 is about 594.2073299310.

The spelling of 209804121 in words is "two hundred nine million, eight hundred four thousand, one hundred twenty-one".