209404921 has 4 divisors (see below), whose sum is σ = 228441744. Its totient is φ = 190368100.

The previous prime is 209404919. The next prime is 209404931. The reversal of 209404921 is 129404902.

It is a happy number.

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 209404921 - 2¹ = 209404919 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209404931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9518395 + ... + 9518416.

It is an arithmetic number, because the mean of its divisors is an integer number (57110436).

Almost surely, 2^209404921 is an apocalyptic number.

It is an amenable number.

209404921 is a deficient number, since it is larger than the sum of its proper divisors (19036823).

209404921 is a wasteful number, since it uses less digits than its factorization.

209404921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19036822.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 209404921 is about 14470.8300038388. The cubic root of 209404921 is about 593.8302191743.

The spelling of 209404921 in words is "two hundred nine million, four hundred four thousand, nine hundred twenty-one".