21917617 has 2 divisors, whose sum is σ = 21917618. Its totient is φ = 21917616.

The previous prime is 21917587. The next prime is 21917627. The reversal of 21917617 is 71671912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21196816 + 720801 = 4604^2 + 849^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21917617 is a prime.

It is not a weakly prime, because it can be changed into another prime (21917627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10958808 + 10958809.

It is an arithmetic number, because the mean of its divisors is an integer number (10958809).

Almost surely, 2^21917617 is an apocalyptic number.

It is an amenable number.

21917617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21917617 is an equidigital number, since it uses as much as digits as its factorization.

21917617 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5292, while the sum is 34.

The square root of 21917617 is about 4681.6254655835. The cubic root of 21917617 is about 279.8537373861.

The spelling of 21917617 in words is "twenty-one million, nine hundred seventeen thousand, six hundred seventeen".