20439209 has 16 divisors (see below), whose sum is σ = 23974656. Its totient is φ = 17064000.

The previous prime is 20439191. The next prime is 20439257. The reversal of 20439209 is 90293402.

It is a cyclic number.

It is not a de Polignac number, because 20439209 - 2¹⁶ = 20373673 is a prime.

It is a super-2 number, since 2×20439209² = 835522529091362, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20439299) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 64319 + ... + 64635.

It is an arithmetic number, because the mean of its divisors is an integer number (1498416).

Almost surely, 2^20439209 is an apocalyptic number.

It is an amenable number.

20439209 is a deficient number, since it is larger than the sum of its proper divisors (3535447).

20439209 is a wasteful number, since it uses less digits than its factorization.

20439209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 536.

The product of its (nonzero) digits is 3888, while the sum is 29.

The square root of 20439209 is about 4520.9743418869. The cubic root of 20439209 is about 273.4143858709.

The spelling of 20439209 in words is "twenty million, four hundred thirty-nine thousand, two hundred nine".