28123661 has 8 divisors (see below), whose sum is σ = 29872440. Its totient is φ = 26385408.

The previous prime is 28123651. The next prime is 28123673. The reversal of 28123661 is 16632182.

It can be written as a sum of positive squares in 4 ways, for example, as 13645636 + 14478025 = 3694^2 + 3805^2 .

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 28123661 - 2¹⁰ = 28122637 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 (28123621) 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 7 ways as a sum of consecutive naturals, for example, 3275 + ... + 8183.

It is an arithmetic number, because the mean of its divisors is an integer number (3734055).

Almost surely, 2^28123661 is an apocalyptic number.

It is an amenable number.

28123661 is a deficient number, since it is larger than the sum of its proper divisors (1748779).

28123661 is a wasteful number, since it uses less digits than its factorization.

28123661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5263.

The product of its digits is 3456, while the sum is 29.

The square root of 28123661 is about 5303.1746152658. The cubic root of 28123661 is about 304.1052735874.

The spelling of 28123661 in words is "twenty-eight million, one hundred twenty-three thousand, six hundred sixty-one".