28217840 has 80 divisors (see below), whose sum is σ = 76870080. Its totient is φ = 9431040.

The previous prime is 28217837. The next prime is 28217851. The reversal of 28217840 is 4871282.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 28217797 and 28217806.

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 22346 + ... + 23574.

It is an arithmetic number, because the mean of its divisors is an integer number (960876).

Almost surely, 2^28217840 is an apocalyptic number.

28217840 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 28217840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38435040).

28217840 is an abundant number, since it is smaller than the sum of its proper divisors (48652240).

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

28217840 is a wasteful number, since it uses less digits than its factorization.

28217840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1290 (or 1284 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 32.

The square root of 28217840 is about 5312.0466865418. The cubic root of 28217840 is about 304.4443524882. Note that the first 3 decimals are identical.

The spelling of 28217840 in words is "twenty-eight million, two hundred seventeen thousand, eight hundred forty".