28640220 has 192 divisors, whose sum is σ = 100101120. Its totient is φ = 5971968.

The previous prime is 28640207. The next prime is 28640231. The reversal of 28640220 is 2204682.

28640220 = 643² + 644² + ... + 705².

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 63 ways as a sum of consecutive naturals, for example, 295212 + ... + 295308.

It is an arithmetic number, because the mean of its divisors is an integer number (521360).

Almost surely, 2^28640220 is an apocalyptic number.

28640220 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 28640220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (50050560).

28640220 is an abundant number, since it is smaller than the sum of its proper divisors (71460900).

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

28640220 is a wasteful number, since it uses less digits than its factorization.

28640220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 172 (or 170 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 24.

The square root of 28640220 is about 5351.6558185294. The cubic root of 28640220 is about 305.9558653080.

The spelling of 28640220 in words is "twenty-eight million, six hundred forty thousand, two hundred twenty".