21108317 has 12 divisors (see below), whose sum is σ = 22433460. Its totient is φ = 19837440.

The previous prime is 21108301. The next prime is 21108323. The reversal of 21108317 is 71380112.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 10310521 + 10797796 = 3211^2 + 3286^2 .

It is not a de Polignac number, because 21108317 - 2⁴ = 21108301 is a prime.

It is a super-2 number, since 2×21108317² = 891122093144978, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21108292 and 21108301.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21108377) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 48533 + ... + 48965.

It is an arithmetic number, because the mean of its divisors is an integer number (1869455).

Almost surely, 2^21108317 is an apocalyptic number.

It is an amenable number.

21108317 is a deficient number, since it is larger than the sum of its proper divisors (1325143).

21108317 is an equidigital number, since it uses as much as digits as its factorization.

21108317 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 544 (or 503 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 21108317 is about 4594.3788481143. The cubic root of 21108317 is about 276.3659510654.

Adding to 21108317 its reverse (71380112), we get a palindrome (92488429).

The spelling of 21108317 in words is "twenty-one million, one hundred eight thousand, three hundred seventeen".