28666640 has 40 divisors (see below), whose sum is σ = 67917528. Its totient is φ = 11248640.

The previous prime is 28666639. The next prime is 28666643. The reversal of 28666640 is 4666682.

It can be written as a sum of positive squares in 4 ways, for example, as 9024016 + 19642624 = 3004^2 + 4432^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 28666594 and 28666603.

It is not an unprimeable number, because it can be changed into a prime (28666643) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 860 + ... + 7620.

Almost surely, 2^28666640 is an apocalyptic number.

28666640 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 28666640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33958764).

28666640 is an abundant number, since it is smaller than the sum of its proper divisors (39250888).

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

28666640 is a wasteful number, since it uses less digits than its factorization.

28666640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6827 (or 6821 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 38.

The square root of 28666640 is about 5354.1236444445. The cubic root of 28666640 is about 306.0499156756.

The spelling of 28666640 in words is "twenty-eight million, six hundred sixty-six thousand, six hundred forty".