21243879 has 12 divisors (see below), whose sum is σ = 30740632. Its totient is φ = 14137200.

The previous prime is 21243857. The next prime is 21243907. The reversal of 21243879 is 97834212.

21243879 is a `hidden beast` number, since 212 + 438 + 7 + 9 = 666.

It is not a de Polignac number, because 21243879 - 2¹⁶ = 21178343 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243779) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 4164 + ... + 7734.

Almost surely, 2^21243879 is an apocalyptic number.

21243879 is a deficient number, since it is larger than the sum of its proper divisors (9496753).

21243879 is a wasteful number, since it uses less digits than its factorization.

21243879 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4238 (or 4235 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 21243879 is about 4609.1082651637. The cubic root of 21243879 is about 276.9563155793.

It can be divided in two parts, 21243 and 879, that added together give a palindrome (22122).

The spelling of 21243879 in words is "twenty-one million, two hundred forty-three thousand, eight hundred seventy-nine".