21005117 has 8 divisors (see below), whose sum is σ = 24085056. Its totient is φ = 17944992.

The previous prime is 21005111. The next prime is 21005123. The reversal of 21005117 is 71150012.

It is an interprime number because it is at equal distance from previous prime (21005111) and next prime (21005123).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21005117 - 2⁶ = 21005053 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21005095 and 21005104.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005111) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2603 + ... + 6984.

It is an arithmetic number, because the mean of its divisors is an integer number (3010632).

Almost surely, 2^21005117 is an apocalyptic number.

It is an amenable number.

21005117 is a deficient number, since it is larger than the sum of its proper divisors (3079939).

21005117 is an equidigital number, since it uses as much as digits as its factorization.

21005117 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9907.

The product of its (nonzero) digits is 70, while the sum is 17.

The square root of 21005117 is about 4583.1339714217. The cubic root of 21005117 is about 275.9148244135.

Adding to 21005117 its reverse (71150012), we get a palindrome (92155129).

The spelling of 21005117 in words is "twenty-one million, five thousand, one hundred seventeen".