647381425781 has 2 divisors, whose sum is σ = 647381425782. Its totient is φ = 647381425780.

The previous prime is 647381425777. The next prime is 647381425811. The reversal of 647381425781 is 187524183746.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 362608708900 + 284772716881 = 602170^2 + 533641^2 .

It is a cyclic number.

It is not a de Polignac number, because 647381425781 - 2² = 647381425777 is a prime.

It is a super-2 number, since 2×647381425781² (a number of 24 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (647381425741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323690712890 + 323690712891.

It is an arithmetic number, because the mean of its divisors is an integer number (323690712891).

Almost surely, 2^647381425781 is an apocalyptic number.

It is an amenable number.

647381425781 is a deficient number, since it is larger than the sum of its proper divisors (1).

647381425781 is an equidigital number, since it uses as much as digits as its factorization.

647381425781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9031680, while the sum is 56.

The spelling of 647381425781 in words is "six hundred forty-seven billion, three hundred eighty-one million, four hundred twenty-five thousand, seven hundred eighty-one".