21617 has 2 divisors, whose sum is σ = 21618. Its totient is φ = 21616.

The previous prime is 21613. The next prime is 21647. The reversal of 21617 is 71612.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15376 + 6241 = 124^2 + 79^2 .

It is a cyclic number.

It is not a de Polignac number, because 21617 - 2² = 21613 is a prime.

It is a Chen prime.

It is equal to p₂₄₂₉ and since 21617 and 2429 have the same sum of digits, it is a Honaker prime.

It is a plaindrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 21595 and 21604.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21617.

It is not a weakly prime, because it can be changed into another prime (21611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10808 + 10809.

It is an arithmetic number, because the mean of its divisors is an integer number (10809).

2²¹⁶¹⁷ is an apocalyptic number.

It is an amenable number.

21617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21617 is an equidigital number, since it uses as much as digits as its factorization.

21617 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 84, while the sum is 17.

The square root of 21617 is about 147.0272083663. The cubic root of 21617 is about 27.8568372904.

The spelling of 21617 in words is "twenty-one thousand, six hundred seventeen".