28117840 has 40 divisors (see below), whose sum is σ = 65897568. Its totient is φ = 11157120.

The previous prime is 28117819. The next prime is 28117871. The reversal of 28117840 is 4871182.

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

It is a super-2 number, since 2×28117840² = 1581225852531200, which contains 22 as substring.

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9139 + ... + 11821.

Almost surely, 2^28117840 is an apocalyptic number.

28117840 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 28117840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32948784).

28117840 is an abundant number, since it is smaller than the sum of its proper divisors (37779728).

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

28117840 is a wasteful number, since it uses less digits than its factorization.

28117840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2827 (or 2821 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 31.

The square root of 28117840 is about 5302.6257646566. The cubic root of 28117840 is about 304.0842910306.

The spelling of 28117840 in words is "twenty-eight million, one hundred seventeen thousand, eight hundred forty".