28766781 has 12 divisors (see below), whose sum is σ = 41717052. Its totient is φ = 19101696.

The previous prime is 28766713. The next prime is 28766783. The reversal of 28766781 is 18766782.

It can be written as a sum of positive squares in 2 ways, for example, as 15327225 + 13439556 = 3915^2 + 3666^2 .

It is a de Polignac number, because none of the positive numbers 2^k-28766781 is a prime.

It is a super-2 number, since 2×28766781² = 1655055378203922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28766783) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3906 + ... + 8531.

It is an arithmetic number, because the mean of its divisors is an integer number (3476421).

Almost surely, 2^28766781 is an apocalyptic number.

It is an amenable number.

28766781 is a deficient number, since it is larger than the sum of its proper divisors (12950271).

28766781 is a wasteful number, since it uses less digits than its factorization.

28766781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12700 (or 12697 counting only the distinct ones).

The product of its digits is 225792, while the sum is 45.

The square root of 28766781 is about 5363.4672554235. The cubic root of 28766781 is about 306.4058756119.

Subtracting from 28766781 its reverse (18766782), we obtain a palindrome (9999999).

The spelling of 28766781 in words is "twenty-eight million, seven hundred sixty-six thousand, seven hundred eighty-one".