21166 has 8 divisors (see below), whose sum is σ = 33480. Its totient is φ = 10008.

The previous prime is 21163. The next prime is 21169. The reversal of 21166 is 66112.

It is an interprime number because it is at equal distance from previous prime (21163) and next prime (21169).

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

It is a nialpdrome in base 13 and base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21163) 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, 241 + ... + 316.

It is an arithmetic number, because the mean of its divisors is an integer number (4185).

2²¹¹⁶⁶ is an apocalyptic number.

21166 is a deficient number, since it is larger than the sum of its proper divisors (12314).

21166 is a wasteful number, since it uses less digits than its factorization.

21166 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 578.

The product of its digits is 72, while the sum is 16.

The square root of 21166 is about 145.4853944559. The cubic root of 21166 is about 27.6617465162.

Adding to 21166 its reverse (66112), we get a palindrome (87278).

It can be divided in two parts, 21 and 166, that multiplied together give a triangular number (3486 = T₈₃).

The spelling of 21166 in words is "twenty-one thousand, one hundred sixty-six".