28018561 has 4 divisors (see below), whose sum is σ = 28180692. Its totient is φ = 27856432.

The previous prime is 28018541. The next prime is 28018579. The reversal of 28018561 is 16581082.

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 26471025 + 1547536 = 5145^2 + 1244^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28018561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28018541) 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, 80806 + ... + 81151.

It is an arithmetic number, because the mean of its divisors is an integer number (7045173).

Almost surely, 2^28018561 is an apocalyptic number.

It is an amenable number.

28018561 is a deficient number, since it is larger than the sum of its proper divisors (162131).

28018561 is a wasteful number, since it uses less digits than its factorization.

28018561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162130.

The product of its (nonzero) digits is 3840, while the sum is 31.

The square root of 28018561 is about 5293.2561812178. The cubic root of 28018561 is about 303.7259801381.

The spelling of 28018561 in words is "twenty-eight million, eighteen thousand, five hundred sixty-one".