28778 has 4 divisors (see below), whose sum is σ = 43170. Its totient is φ = 14388.

The previous prime is 28771. The next prime is 28789. The reversal of 28778 is 87782.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87782 = 2 ⋅43891.

It can be written as a sum of positive squares in only one way, i.e., 26569 + 2209 = 163^2 + 47^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (28771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7193 + ... + 7196.

2²⁸⁷⁷⁸ is an apocalyptic number.

28778 is a deficient number, since it is larger than the sum of its proper divisors (14392).

28778 is a wasteful number, since it uses less digits than its factorization.

28778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14391.

The product of its digits is 6272, while the sum is 32.

The square root of 28778 is about 169.6407969800. The cubic root of 28778 is about 30.6445703040.

The spelling of 28778 in words is "twenty-eight thousand, seven hundred seventy-eight".