687073781 has 2 divisors, whose sum is σ = 687073782. Its totient is φ = 687073780.

The previous prime is 687073729. The next prime is 687073789. The reversal of 687073781 is 187370786.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 678133681 + 8940100 = 26041^2 + 2990^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-687073781 is a prime.

It is a super-2 number, since 2×687073781² = 944140761075271922, which 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 (687073789) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343536890 + 343536891.

It is an arithmetic number, because the mean of its divisors is an integer number (343536891).

Almost surely, 2^687073781 is an apocalyptic number.

It is an amenable number.

687073781 is a deficient number, since it is larger than the sum of its proper divisors (1).

687073781 is an equidigital number, since it uses as much as digits as its factorization.

687073781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 395136, while the sum is 47.

The square root of 687073781 is about 26212.0922667383. The cubic root of 687073781 is about 882.4046580626.

The spelling of 687073781 in words is "six hundred eighty-seven million, seventy-three thousand, seven hundred eighty-one".