687907991 has 2 divisors, whose sum is σ = 687907992. Its totient is φ = 687907990.

The previous prime is 687907931. The next prime is 687908003. The reversal of 687907991 is 199709786.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-687907991 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (687907931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343953995 + 343953996.

It is an arithmetic number, because the mean of its divisors is an integer number (343953996).

Almost surely, 2^687907991 is an apocalyptic number.

687907991 is a deficient number, since it is larger than the sum of its proper divisors (1).

687907991 is an equidigital number, since it uses as much as digits as its factorization.

687907991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1714608, while the sum is 56.

The square root of 687907991 is about 26228.0001334452. Note that the first 3 decimals coincide. The cubic root of 687907991 is about 882.7616372279.

The spelling of 687907991 in words is "six hundred eighty-seven million, nine hundred seven thousand, nine hundred ninety-one".