8125781 has 2 divisors, whose sum is σ = 8125782. Its totient is φ = 8125780.

The previous prime is 8125759. The next prime is 8125811. The reversal of 8125781 is 1875218.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4165681 + 3960100 = 2041^2 + 1990^2 .

It is a cyclic number.

It is not a de Polignac number, because 8125781 - 2¹⁰ = 8124757 is a prime.

It is a super-2 number, since 2×8125781² = 132056633719922, which contains 22 as substring.

It is a Sophie Germain prime.

It is an Ulam number.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8125081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4062890 + 4062891.

It is an arithmetic number, because the mean of its divisors is an integer number (4062891).

Almost surely, 2^8125781 is an apocalyptic number.

It is an amenable number.

8125781 is a deficient number, since it is larger than the sum of its proper divisors (1).

8125781 is an equidigital number, since it uses as much as digits as its factorization.

8125781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4480, while the sum is 32.

The square root of 8125781 is about 2850.5755559185. The cubic root of 8125781 is about 201.0427291319.

The spelling of 8125781 in words is "eight million, one hundred twenty-five thousand, seven hundred eighty-one".