21981104565505 has 16 divisors (see below), whose sum is σ = 26442982121040. Its totient is φ = 17541116347392.

The previous prime is 21981104565503. The next prime is 21981104565533. The reversal of 21981104565505 is 50556540118912.

It can be written as a sum of positive squares in 8 ways, for example, as 293045747569 + 21688058817936 = 541337^2 + 4657044^2 .

It is a cyclic number.

It is not a de Polignac number, because 21981104565505 - 2¹ = 21981104565503 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21981104565503) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48685557 + ... + 49134973.

It is an arithmetic number, because the mean of its divisors is an integer number (1652686382565).

Almost surely, 2^{21981104565505} is an apocalyptic number.

It is an amenable number.

21981104565505 is a deficient number, since it is larger than the sum of its proper divisors (4461877555535).

21981104565505 is a wasteful number, since it uses less digits than its factorization.

21981104565505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 473748.

The product of its (nonzero) digits is 2160000, while the sum is 52.

The spelling of 21981104565505 in words is "twenty-one trillion, nine hundred eighty-one billion, one hundred four million, five hundred sixty-five thousand, five hundred five".