20205401691 has 4 divisors (see below), whose sum is σ = 26940535592. Its totient is φ = 13470267792.

The previous prime is 20205401651. The next prime is 20205401707. The reversal of 20205401691 is 19610450202.

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

It is not a de Polignac number, because 20205401691 - 2⁷ = 20205401563 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20205401611) 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, 3367566946 + ... + 3367566951.

It is an arithmetic number, because the mean of its divisors is an integer number (6735133898).

Almost surely, 2^20205401691 is an apocalyptic number.

20205401691 is a deficient number, since it is larger than the sum of its proper divisors (6735133901).

20205401691 is an equidigital number, since it uses as much as digits as its factorization.

20205401691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6735133900.

The product of its (nonzero) digits is 4320, while the sum is 30.

Adding to 20205401691 its reverse (19610450202), we get a palindrome (39815851893).

The spelling of 20205401691 in words is "twenty billion, two hundred five million, four hundred one thousand, six hundred ninety-one".