687751 has 4 divisors (see below), whose sum is σ = 702432. Its totient is φ = 673072.

The previous prime is 687749. The next prime is 687767. The reversal of 687751 is 157786.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 157786 = 2 ⋅78893.

It is a cyclic number.

It is not a de Polignac number, because 687751 - 2¹ = 687749 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (687721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7270 + ... + 7363.

It is an arithmetic number, because the mean of its divisors is an integer number (175608).

2⁶⁸⁷⁷⁵¹ is an apocalyptic number.

687751 is the 525-th centered pentagonal number.

687751 is a deficient number, since it is larger than the sum of its proper divisors (14681).

687751 is a wasteful number, since it uses less digits than its factorization.

687751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14680.

The product of its digits is 11760, while the sum is 34.

The square root of 687751 is about 829.3075424714. The cubic root of 687751 is about 88.2694478937.

The spelling of 687751 in words is "six hundred eighty-seven thousand, seven hundred fifty-one".