28121808 has 160 divisors (see below), whose sum is σ = 90744192. Its totient is φ = 7372800.

The previous prime is 28121803. The next prime is 28121827. The reversal of 28121808 is 80812182.

It is a Cunningham number, because it is equal to 5303²-1.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28121803) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 116568 + ... + 116808.

Almost surely, 2^28121808 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 28121808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45372096).

28121808 is an abundant number, since it is smaller than the sum of its proper divisors (62622384).

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

28121808 is a wasteful number, since it uses less digits than its factorization.

28121808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293 (or 287 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 30.

The square root of 28121808 is about 5302.9999057137. Note that the first 4 decimals coincide. The cubic root of 28121808 is about 304.0985945204.

The spelling of 28121808 in words is "twenty-eight million, one hundred twenty-one thousand, eight hundred eight".