28333381 has 4 divisors (see below), whose sum is σ = 28540332. Its totient is φ = 28126432.

The previous prime is 28333369. The next prime is 28333391. The reversal of 28333381 is 18333382.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19660356 + 8673025 = 4434^2 + 2945^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28333381 is a prime.

It is a super-2 number, since 2×28333381² = 1605560957782322, 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 a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28333301) 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, 103270 + ... + 103543.

It is an arithmetic number, because the mean of its divisors is an integer number (7135083).

Almost surely, 2^28333381 is an apocalyptic number.

It is an amenable number.

28333381 is a deficient number, since it is larger than the sum of its proper divisors (206951).

28333381 is a wasteful number, since it uses less digits than its factorization.

28333381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 206950.

The product of its digits is 10368, while the sum is 31.

The square root of 28333381 is about 5322.9109517256. The cubic root of 28333381 is about 304.8593134192.

Subtracting from 28333381 its reverse (18333382), we obtain a palindrome (9999999).

The spelling of 28333381 in words is "twenty-eight million, three hundred thirty-three thousand, three hundred eighty-one".