21207 has 4 divisors (see below), whose sum is σ = 28280. Its totient is φ = 14136.

The previous prime is 21193. The next prime is 21211. The reversal of 21207 is 70212.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21207 - 2⁴ = 21191 is a prime.

It is a D-number.

It is a Duffinian number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 21192 and 21201.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21207.

It is not an unprimeable number, because it can be changed into a prime (21227) 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, 3532 + ... + 3537.

It is an arithmetic number, because the mean of its divisors is an integer number (7070).

2²¹²⁰⁷ is an apocalyptic number.

21207 is a deficient number, since it is larger than the sum of its proper divisors (7073).

21207 is an equidigital number, since it uses as much as digits as its factorization.

21207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7072.

The product of its (nonzero) digits is 28, while the sum is 12.

The square root of 21207 is about 145.6262339004. The cubic root of 21207 is about 27.6795958989.

Adding to 21207 its reverse (70212), we get a palindrome (91419).

The spelling of 21207 in words is "twenty-one thousand, two hundred seven", and thus it is an iban number.