28705680 has 60 divisors (see below), whose sum is σ = 96405660. Its totient is φ = 7654656.

The previous prime is 28705669. The next prime is 28705687. The reversal of 28705680 is 8650782.

28705680 is a `hidden beast` number, since 28 + 70 + 568 + 0 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 13307904 + 15397776 = 3648^2 + 3924^2 .

It is a tau number, because it is divible by the number of its divisors (60).

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

It is a nialpdrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (28705687) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19215 + ... + 20654.

It is an arithmetic number, because the mean of its divisors is an integer number (1606761).

Almost surely, 2^28705680 is an apocalyptic number.

28705680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28705680 is an abundant number, since it is smaller than the sum of its proper divisors (67699980).

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

28705680 is a wasteful number, since it uses less digits than its factorization.

28705680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39888 (or 39879 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The square root of 28705680 is about 5357.7681920740. The cubic root of 28705680 is about 306.1887852104.

The spelling of 28705680 in words is "twenty-eight million, seven hundred five thousand, six hundred eighty".