21717613 has 2 divisors, whose sum is σ = 21717614. Its totient is φ = 21717612.

The previous prime is 21717601. The next prime is 21717617. The reversal of 21717613 is 31671712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20629764 + 1087849 = 4542^2 + 1043^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21717613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21717617) 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, 10858806 + 10858807.

It is an arithmetic number, because the mean of its divisors is an integer number (10858807).

Almost surely, 2^21717613 is an apocalyptic number.

It is an amenable number.

21717613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21717613 is an equidigital number, since it uses as much as digits as its factorization.

21717613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1764, while the sum is 28.

The square root of 21717613 is about 4660.2159821193. The cubic root of 21717613 is about 278.9998886619. Note that the first 3 decimals are identical.

The spelling of 21717613 in words is "twenty-one million, seven hundred seventeen thousand, six hundred thirteen".