21285879 has 8 divisors (see below), whose sum is σ = 29615232. Its totient is φ = 13573560.

The previous prime is 21285857. The next prime is 21285893. The reversal of 21285879 is 97858212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21285879 - 2⁹ = 21285367 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21285879.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21285079) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 154177 + ... + 154314.

It is an arithmetic number, because the mean of its divisors is an integer number (3701904).

Almost surely, 2^21285879 is an apocalyptic number.

21285879 is a deficient number, since it is larger than the sum of its proper divisors (8329353).

21285879 is a wasteful number, since it uses less digits than its factorization.

21285879 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 308517.

The product of its digits is 80640, while the sum is 42.

The square root of 21285879 is about 4613.6622113024. The cubic root of 21285879 is about 277.1387133406.

The spelling of 21285879 in words is "twenty-one million, two hundred eighty-five thousand, eight hundred seventy-nine".