21168517 has 2 divisors, whose sum is σ = 21168518. Its totient is φ = 21168516.

The previous prime is 21168509. The next prime is 21168523. The reversal of 21168517 is 71586112.

21168517 is nontrivially palindromic in base 2.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11737476 + 9431041 = 3426^2 + 3071^2 .

It is a cyclic number.

It is not a de Polignac number, because 21168517 - 2³ = 21168509 is a prime.

It is a super-2 number, since 2×21168517² = 896212223958578, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21168547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10584258 + 10584259.

It is an arithmetic number, because the mean of its divisors is an integer number (10584259).

Almost surely, 2^21168517 is an apocalyptic number.

It is an amenable number.

21168517 is a deficient number, since it is larger than the sum of its proper divisors (1).

21168517 is an equidigital number, since it uses as much as digits as its factorization.

21168517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3360, while the sum is 31.

The square root of 21168517 is about 4600.9256677325. The cubic root of 21168517 is about 276.6284295796.

The spelling of 21168517 in words is "twenty-one million, one hundred sixty-eight thousand, five hundred seventeen".