21284538 has 64 divisors (see below), whose sum is σ = 48881664. Its totient is φ = 6120000.

The previous prime is 21284533. The next prime is 21284551. The reversal of 21284538 is 83548212.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a junction number, because it is equal to n+sod(n) for n = 21284499 and 21284508.

It is not an unprimeable number, because it can be changed into a prime (21284533) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 206595 + ... + 206697.

It is an arithmetic number, because the mean of its divisors is an integer number (763776).

Almost surely, 2^21284538 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21284538, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24440832).

21284538 is an abundant number, since it is smaller than the sum of its proper divisors (27597126).

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

21284538 is a wasteful number, since it uses less digits than its factorization.

21284538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 251.

The product of its digits is 15360, while the sum is 33.

The square root of 21284538 is about 4613.5168797784. The cubic root of 21284538 is about 277.1328933504.

It can be divided in two parts, 2128 and 4538, that added together give a palindrome (6666).

The spelling of 21284538 in words is "twenty-one million, two hundred eighty-four thousand, five hundred thirty-eight".