28381666 has 4 divisors (see below), whose sum is σ = 42572502. Its totient is φ = 14190832.

The previous prime is 28381663. The next prime is 28381667. The reversal of 28381666 is 66618382.

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., 18275625 + 10106041 = 4275^2 + 3179^2 .

It is not an unprimeable number, because it can be changed into a prime (28381663) 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 as a sum of consecutive naturals, namely, 7095415 + ... + 7095418.

Almost surely, 2^28381666 is an apocalyptic number.

28381666 is a deficient number, since it is larger than the sum of its proper divisors (14190836).

28381666 is a wasteful number, since it uses less digits than its factorization.

28381666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14190835.

The product of its digits is 82944, while the sum is 40.

The square root of 28381666 is about 5327.4446031845. Note that the first 3 decimals coincide. The cubic root of 28381666 is about 305.0323928688.

The spelling of 28381666 in words is "twenty-eight million, three hundred eighty-one thousand, six hundred sixty-six".