28195781 has 2 divisors, whose sum is σ = 28195782. Its totient is φ = 28195780.

The previous prime is 28195763. The next prime is 28195807. The reversal of 28195781 is 18759182.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27394756 + 801025 = 5234^2 + 895^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28195781 is a prime.

It is a super-2 number, since 2×28195781² = 1590004132399922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28195711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14097890 + 14097891.

It is an arithmetic number, because the mean of its divisors is an integer number (14097891).

Almost surely, 2^28195781 is an apocalyptic number.

It is an amenable number.

28195781 is a deficient number, since it is larger than the sum of its proper divisors (1).

28195781 is an equidigital number, since it uses as much as digits as its factorization.

28195781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 40320, while the sum is 41.

The square root of 28195781 is about 5309.9699622503. The cubic root of 28195781 is about 304.3649997487.

The spelling of 28195781 in words is "twenty-eight million, one hundred ninety-five thousand, seven hundred eighty-one".