28457640 has 96 divisors (see below), whose sum is σ = 93323880. Its totient is φ = 7520256.

The previous prime is 28457633. The next prime is 28457641. The reversal of 28457640 is 4675482.

28457640 is a `hidden beast` number, since 2 + 8 + 4 + 5 + 7 + 640 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 28323684 + 133956 = 5322^2 + 366^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 28457595 and 28457604.

It is not an unprimeable number, because it can be changed into a prime (28457641) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 49032 + ... + 49608.

Almost surely, 2^28457640 is an apocalyptic number.

28457640 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 28457640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46661940).

28457640 is an abundant number, since it is smaller than the sum of its proper divisors (64866240).

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

28457640 is a wasteful number, since it uses less digits than its factorization.

28457640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 731 (or 724 counting only the distinct ones).

The product of its (nonzero) digits is 53760, while the sum is 36.

The square root of 28457640 is about 5334.5702732273. The cubic root of 28457640 is about 305.3043276138.

The spelling of 28457640 in words is "twenty-eight million, four hundred fifty-seven thousand, six hundred forty".