28181891 has 2 divisors, whose sum is σ = 28181892. Its totient is φ = 28181890.

The previous prime is 28181863. The next prime is 28181897. The reversal of 28181891 is 19818182.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28181891 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (28181897) 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 as a sum of consecutive naturals, namely, 14090945 + 14090946.

It is an arithmetic number, because the mean of its divisors is an integer number (14090946).

Almost surely, 2^28181891 is an apocalyptic number.

28181891 is a deficient number, since it is larger than the sum of its proper divisors (1).

28181891 is an equidigital number, since it uses as much as digits as its factorization.

28181891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9216, while the sum is 38.

The square root of 28181891 is about 5308.6618841286. The cubic root of 28181891 is about 304.3150120780.

The spelling of 28181891 in words is "twenty-eight million, one hundred eighty-one thousand, eight hundred ninety-one".