21117 has 4 divisors (see below), whose sum is σ = 28160. Its totient is φ = 14076.

The previous prime is 21107. The next prime is 21121. The reversal of 21117 is 71112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21117 - 2⁴ = 21101 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21107) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3517 + ... + 3522.

It is an arithmetic number, because the mean of its divisors is an integer number (7040).

2²¹¹¹⁷ is an apocalyptic number.

It is an amenable number.

21117 is a deficient number, since it is larger than the sum of its proper divisors (7043).

21117 is an equidigital number, since it uses as much as digits as its factorization.

21117 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7042.

The product of its digits is 14, while the sum is 12.

The square root of 21117 is about 145.3168950948. The cubic root of 21117 is about 27.6403840658.

Adding to 21117 its reverse (71112), we get a palindrome (92229).

The spelling of 21117 in words is "twenty-one thousand, one hundred seventeen", and thus it is an iban number.