21279828 has 12 divisors (see below), whose sum is σ = 49652960. Its totient is φ = 7093272.

The previous prime is 21279827. The next prime is 21279833. The reversal of 21279828 is 82897212.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21279827) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 886648 + ... + 886671.

Almost surely, 2^21279828 is an apocalyptic number.

It is an amenable number.

21279828 is an abundant number, since it is smaller than the sum of its proper divisors (28373132).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21279828 is a wasteful number, since it uses less digits than its factorization.

21279828 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1773326 (or 1773324 counting only the distinct ones).

The product of its digits is 32256, while the sum is 39.

The square root of 21279828 is about 4613.0063949663. The cubic root of 21279828 is about 277.1124498369.

The spelling of 21279828 in words is "twenty-one million, two hundred seventy-nine thousand, eight hundred twenty-eight".