21042317 has 2 divisors, whose sum is σ = 21042318. Its totient is φ = 21042316.

The previous prime is 21042293. The next prime is 21042319. The reversal of 21042317 is 71324012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20967241 + 75076 = 4579^2 + 274^2 .

It is a cyclic number.

It is not a de Polignac number, because 21042317 - 2¹⁸ = 20780173 is a prime.

Together with 21042319, it forms a pair of twin primes.

It is a Chen prime.

It is a plaindrome in base 13.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21042319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521158 + 10521159.

It is an arithmetic number, because the mean of its divisors is an integer number (10521159).

Almost surely, 2^21042317 is an apocalyptic number.

It is an amenable number.

21042317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21042317 is an equidigital number, since it uses as much as digits as its factorization.

21042317 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 21042317 is about 4587.1905345211. The cubic root of 21042317 is about 276.0776097995.

Adding to 21042317 its reverse (71324012), we get a palindrome (92366329).

The spelling of 21042317 in words is "twenty-one million, forty-two thousand, three hundred seventeen".