28021778 has 8 divisors (see below), whose sum is σ = 43057980. Its totient is φ = 13669120.

The previous prime is 28021771. The next prime is 28021781. The reversal of 28021778 is 87712082.

It can be written as a sum of positive squares in 2 ways, for example, as 28015849 + 5929 = 5293^2 + 77^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (28021771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 170783 + ... + 170946.

Almost surely, 2^28021778 is an apocalyptic number.

28021778 is a deficient number, since it is larger than the sum of its proper divisors (15036202).

28021778 is a wasteful number, since it uses less digits than its factorization.

28021778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 341772.

The product of its (nonzero) digits is 12544, while the sum is 35.

The square root of 28021778 is about 5293.5600497208. The cubic root of 28021778 is about 303.7376039695.

The spelling of 28021778 in words is "twenty-eight million, twenty-one thousand, seven hundred seventy-eight".