20409209 has 2 divisors, whose sum is σ = 20409210. Its totient is φ = 20409208.

The previous prime is 20409203. The next prime is 20409217. The reversal of 20409209 is 90290402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10705984 + 9703225 = 3272^2 + 3115^2 .

It is a cyclic number.

It is not a de Polignac number, because 20409209 - 2¹² = 20405113 is a prime.

It is not a weakly prime, because it can be changed into another prime (20409203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10204604 + 10204605.

It is an arithmetic number, because the mean of its divisors is an integer number (10204605).

Almost surely, 2^20409209 is an apocalyptic number.

It is an amenable number.

20409209 is a deficient number, since it is larger than the sum of its proper divisors (1).

20409209 is an equidigital number, since it uses as much as digits as its factorization.

20409209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 20409209 is about 4517.6552546647. The cubic root of 20409209 is about 273.2805508167.

The spelling of 20409209 in words is "twenty million, four hundred nine thousand, two hundred nine".