21124 has 6 divisors (see below), whose sum is σ = 36974. Its totient is φ = 10560.

The previous prime is 21121. The next prime is 21139. The reversal of 21124 is 42112.

It can be written as a sum of positive squares in only one way, i.e., 14400 + 6724 = 120^2 + 82^2 .

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

It is a plaindrome in base 5 and base 14.

It is a zygodrome in base 5.

It is a self number, because there is not a number n which added to its sum of digits gives 21124.

It is not an unprimeable number, because it can be changed into a prime (21121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2637 + ... + 2644.

2²¹¹²⁴ is an apocalyptic number.

It is an amenable number.

21124 is a deficient number, since it is larger than the sum of its proper divisors (15850).

21124 is a wasteful number, since it uses less digits than its factorization.

21124 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5285 (or 5283 counting only the distinct ones).

The product of its digits is 16, while the sum is 10.

The square root of 21124 is about 145.3409783922. The cubic root of 21124 is about 27.6434378663.

Adding to 21124 its reverse (42112), we get a palindrome (63236).

It can be divided in two parts, 2112 and 4, that multiplied together give a palindrome (8448).

The spelling of 21124 in words is "twenty-one thousand, one hundred twenty-four", and thus it is an iban number.