687 has 4 divisors (see below), whose sum is σ = 920. Its totient is φ = 456.

The previous prime is 683. The next prime is 691. The reversal of 687 is 786.

Subtracting from 687 its sum of digits (21), we obtain a palindrome (666).

Subtracting from 687 its product of digits (336), we obtain a triangular number (351 = T_{26}).

Subtracting 687 from its reverse (786), we obtain a palindrome (99).

687 is nontrivially palindromic in base 11.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (683) and next prime (691).

It is not a de Polignac number, because 687 - 2^{2} = 683 is a prime.

It is a D-number.

It is a Duffinian number.

687 is an undulating number in base 11.

It is a plaindrome in base 4, base 8 and base 16.

It is a nialpdrome in base 3 and base 9.

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 112 + ... + 117.

It is an arithmetic number, because the mean of its divisors is an integer number (230).

687 is a deficient number, since it is larger than the sum of its proper divisors (233).

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

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

The sum of its prime factors is 232.

The product of its digits is 336, while the sum is 21.

The square root of 687 is about 26.2106848442. The cubic root of 687 is about 8.8237307144.

The spelling of 687 in words is "six hundred eighty-seven", and thus it is an aban number and an oban number.

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