28121840 has 40 divisors (see below), whose sum is σ = 65829120. Its totient is φ = 11172096.

The previous prime is 28121827. The next prime is 28121857. The reversal of 28121840 is 4812182.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11441 + ... + 13679.

It is an arithmetic number, because the mean of its divisors is an integer number (1645728).

Almost surely, 2^28121840 is an apocalyptic number.

28121840 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 28121840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32914560).

28121840 is an abundant number, since it is smaller than the sum of its proper divisors (37707280).

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

28121840 is a wasteful number, since it uses less digits than its factorization.

28121840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2409 (or 2403 counting only the distinct ones).

The product of its (nonzero) digits is 1024, while the sum is 26.

The square root of 28121840 is about 5303.0029228730. The cubic root of 28121840 is about 304.0987098657.

The spelling of 28121840 in words is "twenty-eight million, one hundred twenty-one thousand, eight hundred forty".