28091440 has 40 divisors (see below), whose sum is σ = 70339248. Its totient is φ = 10371840.

The previous prime is 28091423. The next prime is 28091447. The reversal of 28091440 is 4419082.

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

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 28091399 and 28091408.

It is not an unprimeable number, because it can be changed into a prime (28091447) 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, 12466 + ... + 14545.

Almost surely, 2^28091440 is an apocalyptic number.

28091440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28091440 is an abundant number, since it is smaller than the sum of its proper divisors (42247808).

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

28091440 is a wasteful number, since it uses less digits than its factorization.

28091440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27037 (or 27031 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 28091440 is about 5300.1358473156. The cubic root of 28091440 is about 303.9890924064.

The spelling of 28091440 in words is "twenty-eight million, ninety-one thousand, four hundred forty".