21164 has 24 divisors (see below), whose sum is σ = 44688. Its totient is φ = 8640.

The previous prime is 21163. The next prime is 21169. The reversal of 21164 is 46112.

It is a nialpdrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21163) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 554 + ... + 590.

It is an arithmetic number, because the mean of its divisors is an integer number (1862).

2²¹¹⁶⁴ is an apocalyptic number.

It is an amenable number.

21164 is an abundant number, since it is smaller than the sum of its proper divisors (23524).

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 (22344).

21164 is a wasteful number, since it uses less digits than its factorization.

21164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65 (or 63 counting only the distinct ones).

The product of its digits is 48, while the sum is 14.

The square root of 21164 is about 145.4785207513. The cubic root of 21164 is about 27.6608752252.

Adding to 21164 its product of digits (48), we get a palindrome (21212).

Adding to 21164 its reverse (46112), we get a palindrome (67276).

It can be divided in two parts, 2116 and 4, that multiplied together give a square (8464 = 92²).

The spelling of 21164 in words is "twenty-one thousand, one hundred sixty-four".