20420391 has 4 divisors (see below), whose sum is σ = 27227192. Its totient is φ = 13613592.

The previous prime is 20420377. The next prime is 20420443. The reversal of 20420391 is 19302402.

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

It is not a de Polignac number, because 20420391 - 2⁵ = 20420359 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 (20420311) 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, 3403396 + ... + 3403401.

It is an arithmetic number, because the mean of its divisors is an integer number (6806798).

Almost surely, 2^20420391 is an apocalyptic number.

20420391 is a deficient number, since it is larger than the sum of its proper divisors (6806801).

20420391 is an equidigital number, since it uses as much as digits as its factorization.

20420391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6806800.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 20420391 is about 4518.8926740962. The cubic root of 20420391 is about 273.3304509247.

Adding to 20420391 its reverse (19302402), we get a palindrome (39722793).

The spelling of 20420391 in words is "twenty million, four hundred twenty thousand, three hundred ninety-one".