20120209 has 4 divisors (see below), whose sum is σ = 20769280. Its totient is φ = 19471140.

The previous prime is 20120207. The next prime is 20120213. The reversal of 20120209 is 90202102.

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 20120209 - 2¹ = 20120207 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20120192 and 20120201.

It is not an unprimeable number, because it can be changed into a prime (20120203) 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, 324489 + ... + 324550.

It is an arithmetic number, because the mean of its divisors is an integer number (5192320).

Almost surely, 2^20120209 is an apocalyptic number.

It is an amenable number.

20120209 is a deficient number, since it is larger than the sum of its proper divisors (649071).

20120209 is an equidigital number, since it uses as much as digits as its factorization.

20120209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 649070.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 20120209 is about 4485.5555954642. Note that the first 4 decimals coincide. The cubic root of 20120209 is about 271.9845047762.

The spelling of 20120209 in words is "twenty million, one hundred twenty thousand, two hundred nine".