8199781 has 2 divisors, whose sum is σ = 8199782. Its totient is φ = 8199780.

The previous prime is 8199769. The next prime is 8199787. The reversal of 8199781 is 1879918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7756225 + 443556 = 2785^2 + 666^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8199781 is a prime.

It is a super-2 number, since 2×8199781² = 134472816895922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8199787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4099890 + 4099891.

It is an arithmetic number, because the mean of its divisors is an integer number (4099891).

Almost surely, 2^8199781 is an apocalyptic number.

It is an amenable number.

8199781 is a deficient number, since it is larger than the sum of its proper divisors (1).

8199781 is an equidigital number, since it uses as much as digits as its factorization.

8199781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 43.

The square root of 8199781 is about 2863.5259733413. The cubic root of 8199781 is about 201.6511723026.

The spelling of 8199781 in words is "eight million, one hundred ninety-nine thousand, seven hundred eighty-one".