20308391 has 4 divisors (see below), whose sum is σ = 20342784. Its totient is φ = 20274000.

The previous prime is 20308367. The next prime is 20308411. The reversal of 20308391 is 19380302.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20308391 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20308391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20308361) 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, 16295 + ... + 17496.

It is an arithmetic number, because the mean of its divisors is an integer number (5085696).

Almost surely, 2^20308391 is an apocalyptic number.

20308391 is a deficient number, since it is larger than the sum of its proper divisors (34393).

20308391 is an equidigital number, since it uses as much as digits as its factorization.

20308391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34392.

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

The square root of 20308391 is about 4506.4832186529. The cubic root of 20308391 is about 272.8298214390.

Adding to 20308391 its reverse (19380302), we get a palindrome (39688693).

The spelling of 20308391 in words is "twenty million, three hundred eight thousand, three hundred ninety-one".