21144 has 16 divisors (see below), whose sum is σ = 52920. Its totient is φ = 7040.

The previous prime is 21143. The next prime is 21149. The reversal of 21144 is 44112.

21144 = T₆₄ + T₆₅ + ... + T₇₂.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21144.

It is not an unprimeable number, because it can be changed into a prime (21143) 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, 417 + ... + 464.

2²¹¹⁴⁴ is an apocalyptic number.

21144 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21144 is an abundant number, since it is smaller than the sum of its proper divisors (31776).

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 (26460).

21144 is a wasteful number, since it uses less digits than its factorization.

21144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 890 (or 886 counting only the distinct ones).

The product of its digits is 32, while the sum is 12.

The square root of 21144 is about 145.4097658343. The cubic root of 21144 is about 27.6521592947.

Subtracting from 21144 its product of digits (32), we obtain a palindrome (21112).

Adding to 21144 its reverse (44112), we get a palindrome (65256).

The spelling of 21144 in words is "twenty-one thousand, one hundred forty-four", and thus it is an iban number.