20205210021 has 4 divisors (see below), whose sum is σ = 26940280032. Its totient is φ = 13470140012.

The previous prime is 20205210001. The next prime is 20205210079. The reversal of 20205210021 is 12001250202.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20205210021 - 2¹⁵ = 20205177253 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20205210001) 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, 3367535001 + ... + 3367535006.

It is an arithmetic number, because the mean of its divisors is an integer number (6735070008).

Almost surely, 2^20205210021 is an apocalyptic number.

It is an amenable number.

20205210021 is a deficient number, since it is larger than the sum of its proper divisors (6735070011).

20205210021 is an equidigital number, since it uses as much as digits as its factorization.

20205210021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6735070010.

The product of its (nonzero) digits is 80, while the sum is 15.

Adding to 20205210021 its reverse (12001250202), we get a palindrome (32206460223).

The spelling of 20205210021 in words is "twenty billion, two hundred five million, two hundred ten thousand, twenty-one".