28221440 has 112 divisors (see below), whose sum is σ = 74313288. Its totient is φ = 10223616.

The previous prime is 28221421. The next prime is 28221451. The reversal of 28221440 is 4412282.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 20647936 + 7573504 = 4544^2 + 2752^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 532454 + ... + 532506.

Almost surely, 2^28221440 is an apocalyptic number.

28221440 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 28221440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37156644).

28221440 is an abundant number, since it is smaller than the sum of its proper divisors (46091848).

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

28221440 is an equidigital number, since it uses as much as digits as its factorization.

28221440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97 (or 73 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 23.

The square root of 28221440 is about 5312.3855281785. The cubic root of 28221440 is about 304.4572988260.

The spelling of 28221440 in words is "twenty-eight million, two hundred twenty-one thousand, four hundred forty".