28904381 has 4 divisors (see below), whose sum is σ = 31532064. Its totient is φ = 26276700.

The previous prime is 28904371. The next prime is 28904411. The reversal of 28904381 is 18340982.

28904381 = 629² + 630² + ... + 694².

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28904381 is a prime.

It is a super-2 number, since 2×28904381² = 1670926481986322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28904341) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1313825 + ... + 1313846.

It is an arithmetic number, because the mean of its divisors is an integer number (7883016).

Almost surely, 2^28904381 is an apocalyptic number.

It is an amenable number.

28904381 is a deficient number, since it is larger than the sum of its proper divisors (2627683).

28904381 is a wasteful number, since it uses less digits than its factorization.

28904381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2627682.

The product of its (nonzero) digits is 13824, while the sum is 35.

The square root of 28904381 is about 5376.2794756225. The cubic root of 28904381 is about 306.8936419584.

It can be divided in two parts, 28 and 904381, that added together give a palindrome (904409).

The spelling of 28904381 in words is "twenty-eight million, nine hundred four thousand, three hundred eighty-one".