28021644 has 144 divisors (see below), whose sum is σ = 88897536. Its totient is φ = 7257600.

The previous prime is 28021639. The next prime is 28021657. The reversal of 28021644 is 44612082.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 132699 + ... + 132909.

It is an arithmetic number, because the mean of its divisors is an integer number (617344).

Almost surely, 2^28021644 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 28021644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44448768).

28021644 is an abundant number, since it is smaller than the sum of its proper divisors (60875892).

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

28021644 is a wasteful number, since it uses less digits than its factorization.

28021644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 276 (or 271 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 28021644 is about 5293.5473928170. The cubic root of 28021644 is about 303.7371198115.

The spelling of 28021644 in words is "twenty-eight million, twenty-one thousand, six hundred forty-four".