210121209 has 20 divisors (see below), whose sum is σ = 330407440. Its totient is φ = 132707160.

The previous prime is 210121199. The next prime is 210121217. The reversal of 210121209 is 902121012.

210121209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 210121209 - 2¹⁶ = 210055673 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 210121191 and 210121200.

It is not an unprimeable number, because it can be changed into a prime (210121259) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 66727 + ... + 69804.

It is an arithmetic number, because the mean of its divisors is an integer number (16520372).

Almost surely, 2^210121209 is an apocalyptic number.

It is an amenable number.

210121209 is a deficient number, since it is larger than the sum of its proper divisors (120286231).

210121209 is a wasteful number, since it uses less digits than its factorization.

210121209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136562 (or 136553 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 18.

The square root of 210121209 is about 14495.5582507194. The cubic root of 210121209 is about 594.5065315093.

The spelling of 210121209 in words is "two hundred ten million, one hundred twenty-one thousand, two hundred nine".