21206 has 8 divisors (see below), whose sum is σ = 33264. Its totient is φ = 10120.

The previous prime is 21193. The next prime is 21211. The reversal of 21206 is 60212.

21206 is nontrivially palindromic in base 5.

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

It is a nialpdrome in base 13.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 185 + ... + 276.

It is an arithmetic number, because the mean of its divisors is an integer number (4158).

2²¹²⁰⁶ is an apocalyptic number.

21206 is a deficient number, since it is larger than the sum of its proper divisors (12058).

21206 is a wasteful number, since it uses less digits than its factorization.

21206 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 486.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21206 is about 145.6228004126. The cubic root of 21206 is about 27.6791608219.

Adding to 21206 its reverse (60212), we get a palindrome (81418).

It can be divided in two parts, 2120 and 6, that multiplied together give a triangular number (12720 = T₁₅₉).

The spelling of 21206 in words is "twenty-one thousand, two hundred six".