21707 has 6 divisors (see below), whose sum is σ = 25308. Its totient is φ = 18564.

The previous prime is 21701. The next prime is 21713. The reversal of 21707 is 70712.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21701) and next prime (21713).

It is not a de Polignac number, because 21707 - 2¹⁴ = 5323 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21707.

It is not an unprimeable number, because it can be changed into a prime (21701) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 173 + ... + 270.

It is an arithmetic number, because the mean of its divisors is an integer number (4218).

2²¹⁷⁰⁷ is an apocalyptic number.

21707 is a deficient number, since it is larger than the sum of its proper divisors (3601).

21707 is an equidigital number, since it uses as much as digits as its factorization.

21707 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 457 (or 450 counting only the distinct ones).

The product of its (nonzero) digits is 98, while the sum is 17.

The square root of 21707 is about 147.3329562589. The cubic root of 21707 is about 27.8954433877.

Subtracting from 21707 its product of nonzero digits (98), we obtain a square (21609 = 147²).

The spelling of 21707 in words is "twenty-one thousand, seven hundred seven", and thus it is an iban number.