21000517 has 2 divisors, whose sum is σ = 21000518. Its totient is φ = 21000516.

The previous prime is 21000509. The next prime is 21000527. The reversal of 21000517 is 71500012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18395521 + 2604996 = 4289^2 + 1614^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000517 - 2³ = 21000509 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21000517.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000527) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500258 + 10500259.

It is an arithmetic number, because the mean of its divisors is an integer number (10500259).

Almost surely, 2^21000517 is an apocalyptic number.

It is an amenable number.

21000517 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000517 is an equidigital number, since it uses as much as digits as its factorization.

21000517 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 70, while the sum is 16.

The square root of 21000517 is about 4582.6321039333. The cubic root of 21000517 is about 275.8946816891.

Adding to 21000517 its reverse (71500012), we get a palindrome (92500529).

The spelling of 21000517 in words is "twenty-one million, five hundred seventeen", and thus it is an aban number.