21287679 has 8 divisors (see below), whose sum is σ = 32438400. Its totient is φ = 12164376.

The previous prime is 21287659. The next prime is 21287681. The reversal of 21287679 is 97678212.

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

It is not a de Polignac number, because 21287679 - 2⁷ = 21287551 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21287679.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287659) 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, 506829 + ... + 506870.

It is an arithmetic number, because the mean of its divisors is an integer number (4054800).

Almost surely, 2^21287679 is an apocalyptic number.

21287679 is a deficient number, since it is larger than the sum of its proper divisors (11150721).

21287679 is a wasteful number, since it uses less digits than its factorization.

21287679 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1013709.

The product of its digits is 84672, while the sum is 42.

The square root of 21287679 is about 4613.8572799774. The cubic root of 21287679 is about 277.1465250237.

The spelling of 21287679 in words is "twenty-one million, two hundred eighty-seven thousand, six hundred seventy-nine".