21044 has 6 divisors (see below), whose sum is σ = 36834. Its totient is φ = 10520.

The previous prime is 21031. The next prime is 21059. The reversal of 21044 is 44012.

It can be written as a sum of positive squares in only one way, i.e., 19600 + 1444 = 140^2 + 38^2 .

It is a congruent number.

It is an unprimeable number.

21044 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2627 + ... + 2634.

It is an arithmetic number, because the mean of its divisors is an integer number (6139).

2²¹⁰⁴⁴ is an apocalyptic number.

It is an amenable number.

21044 is a deficient number, since it is larger than the sum of its proper divisors (15790).

21044 is a wasteful number, since it uses less digits than its factorization.

21044 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5265 (or 5263 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 11.

The square root of 21044 is about 145.0655024463. The cubic root of 21044 is about 27.6084969988.

Subtracting from 21044 its product of nonzero digits (32), we obtain a palindrome (21012).

Adding to 21044 its reverse (44012), we get a palindrome (65056).

The spelling of 21044 in words is "twenty-one thousand, forty-four", and thus it is an iban number.