209478121 has 4 divisors (see below), whose sum is σ = 209507200. Its totient is φ = 209449044.

The previous prime is 209478109. The next prime is 209478161. The reversal of 209478121 is 121874902.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 209478121 - 2⁷ = 209477993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209478161) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5200 + ... + 21118.

It is an arithmetic number, because the mean of its divisors is an integer number (52376800).

Almost surely, 2^209478121 is an apocalyptic number.

It is an amenable number.

209478121 is a deficient number, since it is larger than the sum of its proper divisors (29079).

209478121 is a wasteful number, since it uses less digits than its factorization.

209478121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29078.

The product of its (nonzero) digits is 8064, while the sum is 34.

The square root of 209478121 is about 14473.3590088825. The cubic root of 209478121 is about 593.8994046036.

The spelling of 209478121 in words is "two hundred nine million, four hundred seventy-eight thousand, one hundred twenty-one".