21606565997593 has 4 divisors (see below), whose sum is σ = 22351619997540. Its totient is φ = 20861511997648.

The previous prime is 21606565997579. The next prime is 21606565997603. The reversal of 21606565997593 is 39579956560612.

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 15249899732544 + 6356666265049 = 3905112^2 + 2521243^2 .

It is a cyclic number.

It is not a de Polignac number, because 21606565997593 - 2¹⁷ = 21606565866521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21606565997503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 372526999930 + ... + 372526999987.

It is an arithmetic number, because the mean of its divisors is an integer number (5587904999385).

Almost surely, 2^{21606565997593} is an apocalyptic number.

It is an amenable number.

21606565997593 is a deficient number, since it is larger than the sum of its proper divisors (745053999947).

21606565997593 is an equidigital number, since it uses as much as digits as its factorization.

21606565997593 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 745053999946.

The product of its (nonzero) digits is 826686000, while the sum is 73.

The spelling of 21606565997593 in words is "twenty-one trillion, six hundred six billion, five hundred sixty-five million, nine hundred ninety-seven thousand, five hundred ninety-three".