20205491 has 4 divisors (see below), whose sum is σ = 20219472. Its totient is φ = 20191512.

The previous prime is 20205487. The next prime is 20205517. The reversal of 20205491 is 19450202.

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

It is a cyclic number.

It is not a de Polignac number, because 20205491 - 2² = 20205487 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20205481) 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, 4535 + ... + 7808.

It is an arithmetic number, because the mean of its divisors is an integer number (5054868).

Almost surely, 2^20205491 is an apocalyptic number.

20205491 is a deficient number, since it is larger than the sum of its proper divisors (13981).

20205491 is a wasteful number, since it uses less digits than its factorization.

20205491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13980.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 20205491 is about 4495.0518350738. The cubic root of 20205491 is about 272.3682431247.

Adding to 20205491 its reverse (19450202), we get a palindrome (39655693).

The spelling of 20205491 in words is "twenty million, two hundred five thousand, four hundred ninety-one".