21243375 has 48 divisors (see below), whose sum is σ = 40008384. Its totient is φ = 10824000.

The previous prime is 21243361. The next prime is 21243403. The reversal of 21243375 is 57334212.

It is not a de Polignac number, because 21243375 - 2⁴ = 21243359 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 25465 + ... + 26285.

It is an arithmetic number, because the mean of its divisors is an integer number (833508).

Almost surely, 2^21243375 is an apocalyptic number.

21243375 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21243375 is a deficient number, since it is larger than the sum of its proper divisors (18765009).

21243375 is a wasteful number, since it uses less digits than its factorization.

21243375 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 865 (or 852 counting only the distinct ones).

The product of its digits is 5040, while the sum is 27.

The square root of 21243375 is about 4609.0535904890. The cubic root of 21243375 is about 276.9541253471.

Adding to 21243375 its reverse (57334212), we get a palindrome (78577587).

The spelling of 21243375 in words is "twenty-one million, two hundred forty-three thousand, three hundred seventy-five".