21615543145205 has 16 divisors (see below), whose sum is σ = 26214355191024. Its totient is φ = 17109602173440.

The previous prime is 21615543145177. The next prime is 21615543145211. The reversal of 21615543145205 is 50254134551612.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 520647390481 + 21094895754724 = 721559^2 + 4592918^2 .

It is not a de Polignac number, because 21615543145205 - 2¹² = 21615543141109 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 60442472 + ... + 60799041.

It is an arithmetic number, because the mean of its divisors is an integer number (1638397199439).

Almost surely, 2^{21615543145205} is an apocalyptic number.

It is an amenable number.

21615543145205 is a deficient number, since it is larger than the sum of its proper divisors (4598812045819).

21615543145205 is a wasteful number, since it uses less digits than its factorization.

21615543145205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121241896.

The product of its (nonzero) digits is 720000, while the sum is 44.

Adding to 21615543145205 its reverse (50254134551612), we get a palindrome (71869677696817).

The spelling of 21615543145205 in words is "twenty-one trillion, six hundred fifteen billion, five hundred forty-three million, one hundred forty-five thousand, two hundred five".