21612635203205 has 4 divisors (see below), whose sum is σ = 25935162243852. Its totient is φ = 17290108162560.

The previous prime is 21612635203153. The next prime is 21612635203207. The reversal of 21612635203205 is 50230253621612.

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 4641275627044 + 16971359576161 = 2154362^2 + 4119631^2 .

It is not a de Polignac number, because 21612635203205 - 2¹² = 21612635199109 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 (21612635203207) 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, 2161263520316 + ... + 2161263520325.

It is an arithmetic number, because the mean of its divisors is an integer number (6483790560963).

Almost surely, 2^{21612635203205} is an apocalyptic number.

It is an amenable number.

21612635203205 is a deficient number, since it is larger than the sum of its proper divisors (4322527040647).

21612635203205 is an equidigital number, since it uses as much as digits as its factorization.

21612635203205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4322527040646.

The product of its (nonzero) digits is 129600, while the sum is 38.

Adding to 21612635203205 its reverse (50230253621612), we get a palindrome (71842888824817).

The spelling of 21612635203205 in words is "twenty-one trillion, six hundred twelve billion, six hundred thirty-five million, two hundred three thousand, two hundred five".