21186 has 24 divisors (see below), whose sum is σ = 50544. Its totient is φ = 6360.

The previous prime is 21179. The next prime is 21187. The reversal of 21186 is 68112.

It is a Smith number, since the sum of its digits (18) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21187) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 145 + ... + 251.

It is an arithmetic number, because the mean of its divisors is an integer number (2106).

2²¹¹⁸⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21186, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25272).

21186 is an abundant number, since it is smaller than the sum of its proper divisors (29358).

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

21186 is a wasteful number, since it uses less digits than its factorization.

21186 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126 (or 123 counting only the distinct ones).

The product of its digits is 96, while the sum is 18.

The square root of 21186 is about 145.5541136485. The cubic root of 21186 is about 27.6704564090.

Adding to 21186 its reverse (68112), we get a palindrome (89298).

The spelling of 21186 in words is "twenty-one thousand, one hundred eighty-six".