21428544 has 56 divisors (see below), whose sum is σ = 57058560. Its totient is φ = 7097344.

The previous prime is 21428531. The next prime is 21428549. The reversal of 21428544 is 44582412.

It is a super-4 number, since 4×21428544⁴ (a number of 30 digits) contains 4444 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21428549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44497 + ... + 44975.

Almost surely, 2^21428544 is an apocalyptic number.

21428544 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21428544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28529280).

21428544 is an abundant number, since it is smaller than the sum of its proper divisors (35630016).

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

21428544 is a wasteful number, since it uses less digits than its factorization.

21428544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 727 (or 717 counting only the distinct ones).

The product of its digits is 10240, while the sum is 30.

The square root of 21428544 is about 4629.0975362375. The cubic root of 21428544 is about 277.7564936344.

The spelling of 21428544 in words is "twenty-one million, four hundred twenty-eight thousand, five hundred forty-four".