21306258205 has 4 divisors (see below), whose sum is σ = 25567509852. Its totient is φ = 17045006560.

The previous prime is 21306258203. The next prime is 21306258313. The reversal of 21306258205 is 50285260312.

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 16152884836 + 5153373369 = 127094^2 + 71787^2 .

It is not a de Polignac number, because 21306258205 - 2¹ = 21306258203 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 (21306258203) 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, 2130625816 + ... + 2130625825.

It is an arithmetic number, because the mean of its divisors is an integer number (6391877463).

Almost surely, 2^21306258205 is an apocalyptic number.

It is an amenable number.

21306258205 is a deficient number, since it is larger than the sum of its proper divisors (4261251647).

21306258205 is an equidigital number, since it uses as much as digits as its factorization.

21306258205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4261251646.

The product of its (nonzero) digits is 28800, while the sum is 34.

The spelling of 21306258205 in words is "twenty-one billion, three hundred six million, two hundred fifty-eight thousand, two hundred five".