28785217 has 4 divisors (see below), whose sum is σ = 28799316. Its totient is φ = 28771120.

The previous prime is 28785193. The next prime is 28785221. The reversal of 28785217 is 71258782.

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 7403841 + 21381376 = 2721^2 + 4624^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28785217 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 28785217.

It is not an unprimeable number, because it can be changed into a prime (28785257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3334 + ... + 8287.

It is an arithmetic number, because the mean of its divisors is an integer number (7199829).

Almost surely, 2^28785217 is an apocalyptic number.

It is an amenable number.

28785217 is a deficient number, since it is larger than the sum of its proper divisors (14099).

28785217 is a wasteful number, since it uses less digits than its factorization.

28785217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14098.

The product of its digits is 62720, while the sum is 40.

The square root of 28785217 is about 5365.1856445048. The cubic root of 28785217 is about 306.4713179057.

It can be divided in two parts, 28785 and 217, that multiplied together give a triangular number (6246345 = T₃₅₃₄).

The spelling of 28785217 in words is "twenty-eight million, seven hundred eighty-five thousand, two hundred seventeen".