28123861 has 2 divisors, whose sum is σ = 28123862. Its totient is φ = 28123860.

The previous prime is 28123859. The next prime is 28123873. The reversal of 28123861 is 16832182.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18326961 + 9796900 = 4281^2 + 3130^2 .

It is a cyclic number.

It is not a de Polignac number, because 28123861 - 2¹ = 28123859 is a prime.

Together with 28123859, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28123561) 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 as a sum of consecutive naturals, namely, 14061930 + 14061931.

It is an arithmetic number, because the mean of its divisors is an integer number (14061931).

Almost surely, 2^28123861 is an apocalyptic number.

It is an amenable number.

28123861 is a deficient number, since it is larger than the sum of its proper divisors (1).

28123861 is an equidigital number, since it uses as much as digits as its factorization.

28123861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4608, while the sum is 31.

The square root of 28123861 is about 5303.1934718620. The cubic root of 28123861 is about 304.1059944622.

It can be divided in two parts, 281 and 23861, that added together give a palindrome (24142).

The spelling of 28123861 in words is "twenty-eight million, one hundred twenty-three thousand, eight hundred sixty-one".