28081138 has 4 divisors (see below), whose sum is σ = 42121710. Its totient is φ = 14040568.

The previous prime is 28081117. The next prime is 28081153. The reversal of 28081138 is 83118082.

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., 22306729 + 5774409 = 4723^2 + 2403^2 .

It is a super-2 number, since 2×28081138² = 1577100622750088, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7020283 + ... + 7020286.

Almost surely, 2^28081138 is an apocalyptic number.

28081138 is a deficient number, since it is larger than the sum of its proper divisors (14040572).

28081138 is a wasteful number, since it uses less digits than its factorization.

28081138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14040571.

The product of its (nonzero) digits is 3072, while the sum is 31.

The square root of 28081138 is about 5299.1638963142. The cubic root of 28081138 is about 303.9519271283.

It can be divided in two parts, 280 and 81138, that added together give a palindrome (81418).

The spelling of 28081138 in words is "twenty-eight million, eighty-one thousand, one hundred thirty-eight".