28821778 has 4 divisors (see below), whose sum is σ = 43232670. Its totient is φ = 14410888.

The previous prime is 28821773. The next prime is 28821781. The reversal of 28821778 is 87712882.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 21187609 + 7634169 = 4603^2 + 2763^2 .

It is not an unprimeable number, because it can be changed into a prime (28821773) 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 as a sum of consecutive naturals, namely, 7205443 + ... + 7205446.

Almost surely, 2^28821778 is an apocalyptic number.

28821778 is a deficient number, since it is larger than the sum of its proper divisors (14410892).

28821778 is a wasteful number, since it uses less digits than its factorization.

28821778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14410891.

The product of its digits is 100352, while the sum is 43.

The square root of 28821778 is about 5368.5918079139. The cubic root of 28821778 is about 306.6010159298.

The spelling of 28821778 in words is "twenty-eight million, eight hundred twenty-one thousand, seven hundred seventy-eight".