21066 has 8 divisors (see below), whose sum is σ = 42144. Its totient is φ = 7020.

The previous prime is 21061. The next prime is 21067. The reversal of 21066 is 66012.

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

21066 is an admirable number.

It is a Smith number, since the sum of its digits (15) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (21061) 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, 1750 + ... + 1761.

It is an arithmetic number, because the mean of its divisors is an integer number (5268).

2²¹⁰⁶⁶ is an apocalyptic number.

21066 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21072).

21066 is a wasteful number, since it uses less digits than its factorization.

21066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3516.

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 21066 is about 145.1413104530. The cubic root of 21066 is about 27.6181145524.

Adding to 21066 its reverse (66012), we get a palindrome (87078).

It can be divided in two parts, 2106 and 6, that added together give a palindrome (2112).

The spelling of 21066 in words is "twenty-one thousand, sixty-six".