20209391 has 4 divisors (see below), whose sum is σ = 20218800. Its totient is φ = 20199984.

The previous prime is 20209381. The next prime is 20209429. The reversal of 20209391 is 19390202.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 20209391 - 2¹⁴ = 20193007 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 20209391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20209381) 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, 275 + ... + 6363.

It is an arithmetic number, because the mean of its divisors is an integer number (5054700).

Almost surely, 2^20209391 is an apocalyptic number.

20209391 is a deficient number, since it is larger than the sum of its proper divisors (9409).

20209391 is an equidigital number, since it uses as much as digits as its factorization.

20209391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9408.

The product of its (nonzero) digits is 972, while the sum is 26.

The square root of 20209391 is about 4495.4856244904. The cubic root of 20209391 is about 272.3857658831.

Adding to 20209391 its reverse (19390202), we get a palindrome (39599593).

It can be divided in two parts, 2020 and 9391, that added together give a palindrome (11411).

The spelling of 20209391 in words is "twenty million, two hundred nine thousand, three hundred ninety-one".