21258243 has 12 divisors (see below), whose sum is σ = 30929080. Its totient is φ = 14069376.

The previous prime is 21258199. The next prime is 21258253. The reversal of 21258243 is 34285212.

It is not a de Polignac number, because 21258243 - 2¹² = 21254147 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21258253) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7246 + ... + 9747.

Almost surely, 2^21258243 is an apocalyptic number.

21258243 is a deficient number, since it is larger than the sum of its proper divisors (9670837).

21258243 is a wasteful number, since it uses less digits than its factorization.

21258243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17138 (or 17135 counting only the distinct ones).

The product of its digits is 3840, while the sum is 27.

The square root of 21258243 is about 4610.6662208405. Note that the first 3 decimals coincide. The cubic root of 21258243 is about 277.0187226416.

The spelling of 21258243 in words is "twenty-one million, two hundred fifty-eight thousand, two hundred forty-three".