21084428 has 6 divisors (see below), whose sum is σ = 36897756. Its totient is φ = 10542212.

The previous prime is 21084419. The next prime is 21084451. The reversal of 21084428 is 82448012.

It is a self number, because there is not a number n which added to its sum of digits gives 21084428.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2635550 + ... + 2635557.

It is an arithmetic number, because the mean of its divisors is an integer number (6149626).

Almost surely, 2^21084428 is an apocalyptic number.

It is an amenable number.

21084428 is a deficient number, since it is larger than the sum of its proper divisors (15813328).

21084428 is a wasteful number, since it uses less digits than its factorization.

21084428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5271111 (or 5271109 counting only the distinct ones).

The product of its (nonzero) digits is 4096, while the sum is 29.

The square root of 21084428 is about 4591.7783047530. The cubic root of 21084428 is about 276.2616541291.

It can be divided in two parts, 21084 and 428, that added together give a palindrome (21512).

The spelling of 21084428 in words is "twenty-one million, eighty-four thousand, four hundred twenty-eight".