210021009 has 32 divisors (see below), whose sum is σ = 326415744. Its totient is φ = 118702080.

The previous prime is 210020989. The next prime is 210021047. The reversal of 210021009 is 900120012.

It is a happy number.

It is not a de Polignac number, because 210021009 - 2⁹ = 210020497 is a prime.

It is not an unprimeable number, because it can be changed into a prime (210021089) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 61737 + ... + 65049.

It is an arithmetic number, because the mean of its divisors is an integer number (10200492).

Almost surely, 2^210021009 is an apocalyptic number.

It is an amenable number.

210021009 is a deficient number, since it is larger than the sum of its proper divisors (116394735).

210021009 is a wasteful number, since it uses less digits than its factorization.

210021009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3457.

The product of its (nonzero) digits is 36, while the sum is 15.

The square root of 210021009 is about 14492.1016074274. The cubic root of 210021009 is about 594.4120161798.

The spelling of 210021009 in words is "two hundred ten million, twenty-one thousand, nine".