28550781 has 36 divisors (see below), whose sum is σ = 48523644. Its totient is φ = 16128000.

The previous prime is 28550779. The next prime is 28550789. The reversal of 28550781 is 18705582.

28550781 is a `hidden beast` number, since 28 + 550 + 7 + 81 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 26687556 + 1863225 = 5166^2 + 1365^2 .

It is not a de Polignac number, because 28550781 - 2¹ = 28550779 is a prime.

It is a super-2 number, since 2×28550781² = 1630294191419922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28550789) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 44221 + ... + 44861.

It is an arithmetic number, because the mean of its divisors is an integer number (1347879).

Almost surely, 2^28550781 is an apocalyptic number.

28550781 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

28550781 is a deficient number, since it is larger than the sum of its proper divisors (19972863).

28550781 is a wasteful number, since it uses less digits than its factorization.

28550781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 762 (or 752 counting only the distinct ones).

The product of its (nonzero) digits is 22400, while the sum is 36.

The square root of 28550781 is about 5343.2930857291. The cubic root of 28550781 is about 305.6370488431.

The spelling of 28550781 in words is "twenty-eight million, five hundred fifty thousand, seven hundred eighty-one".