21406528 has 56 divisors (see below), whose sum is σ = 49926240. Its totient is φ = 8977920.

The previous prime is 21406507. The next prime is 21406529. The reversal of 21406528 is 82560412.

It is a junction number, because it is equal to n+sod(n) for n = 21406496 and 21406505.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21406529) 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, 7983 + ... + 10321.

It is an arithmetic number, because the mean of its divisors is an integer number (891540).

Almost surely, 2^21406528 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21406528, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24963120).

21406528 is an abundant number, since it is smaller than the sum of its proper divisors (28519712).

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

21406528 is a wasteful number, since it uses less digits than its factorization.

21406528 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2375 (or 2365 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 28.

The square root of 21406528 is about 4626.7189238163. The cubic root of 21406528 is about 277.6613373419.

It can be divided in two parts, 2140 and 6528, that added together give a palindrome (8668).

The spelling of 21406528 in words is "twenty-one million, four hundred six thousand, five hundred twenty-eight".