687817391 has 2 divisors, whose sum is σ = 687817392. Its totient is φ = 687817390.

The previous prime is 687817387. The next prime is 687817451. The reversal of 687817391 is 193718786.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 687817391 - 2² = 687817387 is a 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 (687817381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343908695 + 343908696.

It is an arithmetic number, because the mean of its divisors is an integer number (343908696).

Almost surely, 2^687817391 is an apocalyptic number.

687817391 is a deficient number, since it is larger than the sum of its proper divisors (1).

687817391 is an equidigital number, since it uses as much as digits as its factorization.

687817391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 508032, while the sum is 50.

The square root of 687817391 is about 26226.2729147700. The cubic root of 687817391 is about 882.7228812137.

The spelling of 687817391 in words is "six hundred eighty-seven million, eight hundred seventeen thousand, three hundred ninety-one".