28431778 has 16 divisors (see below), whose sum is σ = 44102520. Its totient is φ = 13737600.

The previous prime is 28431763. The next prime is 28431779. The reversal of 28431778 is 87713482.

It can be written as a sum of positive squares in 4 ways, for example, as 13010449 + 15421329 = 3607^2 + 3927^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 28431778.

It is not an unprimeable number, because it can be changed into a prime (28431779) 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 7 ways as a sum of consecutive naturals, for example, 7348 + ... + 10528.

Almost surely, 2^28431778 is an apocalyptic number.

28431778 is a deficient number, since it is larger than the sum of its proper divisors (15670742).

28431778 is a wasteful number, since it uses less digits than its factorization.

28431778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3333.

The product of its digits is 75264, while the sum is 40.

The square root of 28431778 is about 5332.1457219397. The cubic root of 28431778 is about 305.2118138097.

The spelling of 28431778 in words is "twenty-eight million, four hundred thirty-one thousand, seven hundred seventy-eight".