28218661 has 8 divisors (see below), whose sum is σ = 29078744. Its totient is φ = 27371520.

The previous prime is 28218637. The next prime is 28218719. The reversal of 28218661 is 16681282.

It can be written as a sum of positive squares in 4 ways, for example, as 65025 + 28153636 = 255^2 + 5306^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 28218661 - 2¹¹ = 28216613 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28218611) 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 7 ways as a sum of consecutive naturals, for example, 1285 + ... + 7621.

It is an arithmetic number, because the mean of its divisors is an integer number (3634843).

Almost surely, 2^28218661 is an apocalyptic number.

It is an amenable number.

28218661 is a deficient number, since it is larger than the sum of its proper divisors (860083).

28218661 is an equidigital number, since it uses as much as digits as its factorization.

28218661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6471.

The product of its digits is 9216, while the sum is 34.

The square root of 28218661 is about 5312.1239631620. The cubic root of 28218661 is about 304.4473050694.

The spelling of 28218661 in words is "twenty-eight million, two hundred eighteen thousand, six hundred sixty-one".