687643121 has 12 divisors (see below), whose sum is σ = 788704896. Its totient is φ = 597948120.

The previous prime is 687643109. The next prime is 687643127. The reversal of 687643121 is 121346786.

It is a de Polignac number, because none of the positive numbers 2^k-687643121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (687643127) 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 in 11 ways as a sum of consecutive naturals, for example, 120761 + ... + 126326.

It is an arithmetic number, because the mean of its divisors is an integer number (65725408).

Almost surely, 2^687643121 is an apocalyptic number.

It is an amenable number.

687643121 is a deficient number, since it is larger than the sum of its proper divisors (101061775).

687643121 is a wasteful number, since it uses less digits than its factorization.

687643121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 247132 (or 247121 counting only the distinct ones).

The product of its digits is 48384, while the sum is 38.

The square root of 687643121 is about 26222.9502726143. The cubic root of 687643121 is about 882.6483240651.

The spelling of 687643121 in words is "six hundred eighty-seven million, six hundred forty-three thousand, one hundred twenty-one".