20508391 has 8 divisors (see below), whose sum is σ = 22284800. Its totient is φ = 18801720.

The previous prime is 20508379. The next prime is 20508413. The reversal of 20508391 is 19380502.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20508391 - 2⁷ = 20508263 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20508791) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16821 + ... + 17998.

It is an arithmetic number, because the mean of its divisors is an integer number (2785600).

Almost surely, 2^20508391 is an apocalyptic number.

20508391 is a deficient number, since it is larger than the sum of its proper divisors (1776409).

20508391 is a wasteful number, since it uses less digits than its factorization.

20508391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34869.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 20508391 is about 4528.6191052019. The cubic root of 20508391 is about 273.7225199857.

Adding to 20508391 its reverse (19380502), we get a palindrome (39888893).

The spelling of 20508391 in words is "twenty million, five hundred eight thousand, three hundred ninety-one".