20205421 has 4 divisors (see below), whose sum is σ = 20214844. Its totient is φ = 20196000.

The previous prime is 20205389. The next prime is 20205467. The reversal of 20205421 is 12450202.

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 can be written as a sum of positive squares in 2 ways, for example, as 3189796 + 17015625 = 1786^2 + 4125^2 .

It is a cyclic number.

It is not a de Polignac number, because 20205421 - 2⁵ = 20205389 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20205395 and 20205404.

It is a congruent 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, 241 + ... + 6361.

It is an arithmetic number, because the mean of its divisors is an integer number (5053711).

Almost surely, 2^20205421 is an apocalyptic number.

It is an amenable number.

20205421 is a deficient number, since it is larger than the sum of its proper divisors (9423).

20205421 is an equidigital number, since it uses as much as digits as its factorization.

20205421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9422.

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 20205421 is about 4495.0440487274. The cubic root of 20205421 is about 272.3679285931.

Adding to 20205421 its reverse (12450202), we get a palindrome (32655623).

The spelling of 20205421 in words is "twenty million, two hundred five thousand, four hundred twenty-one".