20508409 has 4 divisors (see below), whose sum is σ = 21714804. Its totient is φ = 19302016.

The previous prime is 20508379. The next prime is 20508413. The reversal of 20508409 is 90480502.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15681600 + 4826809 = 3960^2 + 2197^2 .

It is a cyclic number.

It is not a de Polignac number, because 20508409 - 2⁷ = 20508281 is a prime.

It is a super-2 number, since 2×20508409² = 841189679422562, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20503409) 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, 603172 + ... + 603205.

It is an arithmetic number, because the mean of its divisors is an integer number (5428701).

Almost surely, 2^20508409 is an apocalyptic number.

It is an amenable number.

20508409 is a deficient number, since it is larger than the sum of its proper divisors (1206395).

20508409 is a wasteful number, since it uses less digits than its factorization.

20508409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1206394.

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 20508409 is about 4528.6210925623. The cubic root of 20508409 is about 273.7226000668.

The spelling of 20508409 in words is "twenty million, five hundred eight thousand, four hundred nine".