21306617 has 2 divisors, whose sum is σ = 21306618. Its totient is φ = 21306616.

The previous prime is 21306587. The next prime is 21306707. The reversal of 21306617 is 71660312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13075456 + 8231161 = 3616^2 + 2869^2 .

It is a cyclic number.

It is not a de Polignac number, because 21306617 - 2¹⁶ = 21241081 is a prime.

It is not a weakly prime, because it can be changed into another prime (21306217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10653308 + 10653309.

It is an arithmetic number, because the mean of its divisors is an integer number (10653309).

Almost surely, 2^21306617 is an apocalyptic number.

It is an amenable number.

21306617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21306617 is an equidigital number, since it uses as much as digits as its factorization.

21306617 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1512, while the sum is 26.

The square root of 21306617 is about 4615.9091195560. The cubic root of 21306617 is about 277.2286859337.

Adding to 21306617 its reverse (71660312), we get a palindrome (92966929).

The spelling of 21306617 in words is "twenty-one million, three hundred six thousand, six hundred seventeen".