21042243 has 24 divisors (see below), whose sum is σ = 32589648. Its totient is φ = 13036032.

The previous prime is 21042223. The next prime is 21042251. The reversal of 21042243 is 34224012.

It is not a de Polignac number, because 21042243 - 2⁹ = 21041731 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21042223) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11871 + ... + 13527.

It is an arithmetic number, because the mean of its divisors is an integer number (1357902).

Almost surely, 2^21042243 is an apocalyptic number.

21042243 is a deficient number, since it is larger than the sum of its proper divisors (11547405).

21042243 is a wasteful number, since it uses less digits than its factorization.

21042243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1763 (or 1760 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 21042243 is about 4587.1824685748. The cubic root of 21042243 is about 276.0772861696.

Adding to 21042243 its reverse (34224012), we get a palindrome (55266255).

The spelling of 21042243 in words is "twenty-one million, forty-two thousand, two hundred forty-three".