28705220 has 12 divisors (see below), whose sum is σ = 60281004. Its totient is φ = 11482080.

The previous prime is 28705217. The next prime is 28705223. The reversal of 28705220 is 2250782.

It is an interprime number because it is at equal distance from previous prime (28705217) and next prime (28705223).

It can be written as a sum of positive squares in 2 ways, for example, as 7929856 + 20775364 = 2816^2 + 4558^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 28705220.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28705223) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 717611 + ... + 717650.

It is an arithmetic number, because the mean of its divisors is an integer number (5023417).

Almost surely, 2^28705220 is an apocalyptic number.

28705220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28705220 is an abundant number, since it is smaller than the sum of its proper divisors (31575784).

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

28705220 is a wasteful number, since it uses less digits than its factorization.

28705220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1435270 (or 1435268 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 26.

The square root of 28705220 is about 5357.7252635797. The cubic root of 28705220 is about 306.1871496735.

The spelling of 28705220 in words is "twenty-eight million, seven hundred five thousand, two hundred twenty".