28821780 has 144 divisors (see below), whose sum is σ = 95855760. Its totient is φ = 6967296.

The previous prime is 28821773. The next prime is 28821781. The reversal of 28821780 is 8712882.

It can be written as a sum of positive squares in 8 ways, for example, as 6411024 + 22410756 = 2532^2 + 4734^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28821781) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 255004 + ... + 255116.

It is an arithmetic number, because the mean of its divisors is an integer number (665665).

Almost surely, 2^28821780 is an apocalyptic number.

28821780 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 28821780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (47927880).

28821780 is an abundant number, since it is smaller than the sum of its proper divisors (67033980).

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

28821780 is a wasteful number, since it uses less digits than its factorization.

28821780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 250 (or 245 counting only the distinct ones).

The product of its (nonzero) digits is 14336, while the sum is 36.

The square root of 28821780 is about 5368.5919941825. The cubic root of 28821780 is about 306.6010230217.

The spelling of 28821780 in words is "twenty-eight million, eight hundred twenty-one thousand, seven hundred eighty".