28378821 has 4 divisors (see below), whose sum is σ = 37838432. Its totient is φ = 18919212.

The previous prime is 28378817. The next prime is 28378829. The reversal of 28378821 is 12887382.

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 not a de Polignac number, because 28378821 - 2² = 28378817 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28378821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28378829) 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, 4729801 + ... + 4729806.

It is an arithmetic number, because the mean of its divisors is an integer number (9459608).

Almost surely, 2^28378821 is an apocalyptic number.

It is an amenable number.

28378821 is a deficient number, since it is larger than the sum of its proper divisors (9459611).

28378821 is an equidigital number, since it uses as much as digits as its factorization.

28378821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9459610.

The product of its digits is 43008, while the sum is 39.

The square root of 28378821 is about 5327.1775829232. The cubic root of 28378821 is about 305.0222003011.

The spelling of 28378821 in words is "twenty-eight million, three hundred seventy-eight thousand, eight hundred twenty-one".