28509840 has 160 divisors (see below), whose sum is σ = 100172160. Its totient is φ = 7451136.

The previous prime is 28509839. The next prime is 28509847. The reversal of 28509840 is 4890582.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 28509795 and 28509804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28509847) 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, 144622 + ... + 144818.

It is an arithmetic number, because the mean of its divisors is an integer number (626076).

Almost surely, 2^28509840 is an apocalyptic number.

28509840 is a gapful number since it is divisible by the number (20) 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 28509840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (50086080).

28509840 is an abundant number, since it is smaller than the sum of its proper divisors (71662320).

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

28509840 is a wasteful number, since it uses less digits than its factorization.

28509840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 286 (or 274 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The square root of 28509840 is about 5339.4606469193. The cubic root of 28509840 is about 305.4908873736.

The spelling of 28509840 in words is "twenty-eight million, five hundred nine thousand, eight hundred forty".