21000717 has 12 divisors (see below), whose sum is σ = 30376060. Its totient is φ = 13981248.

The previous prime is 21000709. The next prime is 21000731. The reversal of 21000717 is 71700012.

It can be written as a sum of positive squares in 2 ways, for example, as 9036036 + 11964681 = 3006^2 + 3459^2 .

It is not a de Polignac number, because 21000717 - 2³ = 21000709 is a prime.

It is a super-2 number, since 2×21000717² = 882060229028178, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21000717.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000737) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9009 + ... + 11097.

Almost surely, 2^21000717 is an apocalyptic number.

It is an amenable number.

21000717 is a deficient number, since it is larger than the sum of its proper divisors (9375343).

21000717 is a wasteful number, since it uses less digits than its factorization.

21000717 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3212 (or 3209 counting only the distinct ones).

The product of its (nonzero) digits is 98, while the sum is 18.

The square root of 21000717 is about 4582.6539254017. The cubic root of 21000717 is about 275.8955575208.

Adding to 21000717 its reverse (71700012), we get a palindrome (92700729).

The spelling of 21000717 in words is "twenty-one million, seven hundred seventeen", and thus it is an aban number.