20001209 has 4 divisors (see below), whose sum is σ = 20035200. Its totient is φ = 19967220.

The previous prime is 20001203. The next prime is 20001217. The reversal of 20001209 is 90210002.

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 a de Polignac number, because none of the positive numbers 2^k-20001209 is a prime.

It is a super-2 number, since 2×20001209² = 800096722923362, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20001193 and 20001202.

It is not an unprimeable number, because it can be changed into a prime (20001203) 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, 16097 + ... + 17294.

It is an arithmetic number, because the mean of its divisors is an integer number (5008800).

Almost surely, 2^20001209 is an apocalyptic number.

It is an amenable number.

20001209 is a deficient number, since it is larger than the sum of its proper divisors (33991).

20001209 is an equidigital number, since it uses as much as digits as its factorization.

20001209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33990.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 20001209 is about 4472.2711232661. The cubic root of 20001209 is about 271.4472311008.

The spelling of 20001209 in words is "twenty million, one thousand, two hundred nine".