21601223355265 has 4 divisors (see below), whose sum is σ = 25921468026324. Its totient is φ = 17280978684208.

The previous prime is 21601223355253. The next prime is 21601223355269. The reversal of 21601223355265 is 56255332210612.

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 3014053626609 + 18587169728656 = 1736103^2 + 4311284^2 .

It is a cyclic number.

It is not a de Polignac number, because 21601223355265 - 2¹¹ = 21601223353217 is a prime.

It is a super-2 number, since 2×21601223355265² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21601223355269) 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, 2160122335522 + ... + 2160122335531.

It is an arithmetic number, because the mean of its divisors is an integer number (6480367006581).

Almost surely, 2^{21601223355265} is an apocalyptic number.

It is an amenable number.

21601223355265 is a deficient number, since it is larger than the sum of its proper divisors (4320244671059).

21601223355265 is an equidigital number, since it uses as much as digits as its factorization.

21601223355265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4320244671058.

The product of its (nonzero) digits is 648000, while the sum is 43.

Adding to 21601223355265 its reverse (56255332210612), we get a palindrome (77856555565877).

The spelling of 21601223355265 in words is "twenty-one trillion, six hundred one billion, two hundred twenty-three million, three hundred fifty-five thousand, two hundred sixty-five".