21617321617 has 4 divisors (see below), whose sum is σ = 21643652916. Its totient is φ = 21590990320.

The previous prime is 21617321591. The next prime is 21617321651. The reversal of 21617321617 is 71612371612.

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 12116725776 + 9500595841 = 110076^2 + 97471^2 .

It is a cyclic number.

It is not a de Polignac number, because 21617321617 - 2¹⁹ = 21616797329 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21617321017) 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, 13164418 + ... + 13166059.

It is an arithmetic number, because the mean of its divisors is an integer number (5410913229).

Almost surely, 2^21617321617 is an apocalyptic number.

It is an amenable number.

21617321617 is a deficient number, since it is larger than the sum of its proper divisors (26331299).

21617321617 is an equidigital number, since it uses as much as digits as its factorization.

21617321617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26331298.

The product of its digits is 21168, while the sum is 37.

The spelling of 21617321617 in words is "twenty-one billion, six hundred seventeen million, three hundred twenty-one thousand, six hundred seventeen".