20408221 has 4 divisors (see below), whose sum is σ = 20742844. Its totient is φ = 20073600.

The previous prime is 20408191. The next prime is 20408231. The reversal of 20408221 is 12280402.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1144900 + 19263321 = 1070^2 + 4389^2 .

It is a cyclic number.

It is not a de Polignac number, because 20408221 - 2⁵ = 20408189 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 (20408231) 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, 167220 + ... + 167341.

It is an arithmetic number, because the mean of its divisors is an integer number (5185711).

Almost surely, 2^20408221 is an apocalyptic number.

It is an amenable number.

20408221 is a deficient number, since it is larger than the sum of its proper divisors (334623).

20408221 is an equidigital number, since it uses as much as digits as its factorization.

20408221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 334622.

The product of its (nonzero) digits is 256, while the sum is 19.

The square root of 20408221 is about 4517.5459045814. The cubic root of 20408221 is about 273.2761409521.

Adding to 20408221 its reverse (12280402), we get a palindrome (32688623).

The spelling of 20408221 in words is "twenty million, four hundred eight thousand, two hundred twenty-one".