21124243 has 6 divisors (see below), whose sum is σ = 24573156. Its totient is φ = 18106452.

The previous prime is 21124199. The next prime is 21124253. The reversal of 21124243 is 34242112.

It is a de Polignac number, because none of the positive numbers 2^k-21124243 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21124243.

It is not an unprimeable number, because it can be changed into a prime (21124253) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 215505 + ... + 215602.

It is an arithmetic number, because the mean of its divisors is an integer number (4095526).

Almost surely, 2^21124243 is an apocalyptic number.

21124243 is a deficient number, since it is larger than the sum of its proper divisors (3448913).

21124243 is an equidigital number, since it uses as much as digits as its factorization.

21124243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 431121 (or 431114 counting only the distinct ones).

The product of its digits is 384, while the sum is 19.

The square root of 21124243 is about 4596.1117262312. Note that the first 3 decimals coincide. The cubic root of 21124243 is about 276.4354386464.

Adding to 21124243 its reverse (34242112), we get a palindrome (55366355).

The spelling of 21124243 in words is "twenty-one million, one hundred twenty-four thousand, two hundred forty-three".