28081890 has 80 divisors (see below), whose sum is σ = 77632632. Its totient is φ = 7278336.

The previous prime is 28081871. The next prime is 28081897. The reversal of 28081890 is 9818082.

It can be written as a sum of positive squares in 4 ways, for example, as 21316689 + 6765201 = 4617^2 + 2601^2 .

It is not an unprimeable number, because it can be changed into a prime (28081897) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 29502 + ... + 30438.

Almost surely, 2^28081890 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 28081890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38816316).

28081890 is an abundant number, since it is smaller than the sum of its proper divisors (49550742).

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

28081890 is a wasteful number, since it uses less digits than its factorization.

28081890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 993 (or 984 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 36.

The square root of 28081890 is about 5299.2348504289. The cubic root of 28081890 is about 303.9546403352.

The spelling of 28081890 in words is "twenty-eight million, eighty-one thousand, eight hundred ninety".