687978 has 24 divisors (see below), whose sum is σ = 1532388. Its totient is φ = 222912.

The previous prime is 687977. The next prime is 688003. The reversal of 687978 is 879786.

It can be written as a sum of positive squares in 2 ways, for example, as 514089 + 173889 = 717^2 + 417^2 .

It is not an unprimeable number, because it can be changed into a prime (687977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 150 + ... + 1182.

2⁶⁸⁷⁹⁷⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 687978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (766194).

687978 is an abundant number, since it is smaller than the sum of its proper divisors (844410).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

687978 is a wasteful number, since it uses less digits than its factorization.

687978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1078 (or 1075 counting only the distinct ones).

The product of its digits is 169344, while the sum is 45.

The square root of 687978 is about 829.4443923495. Note that the first 3 decimals coincide. The cubic root of 687978 is about 88.2791582688.

The spelling of 687978 in words is "six hundred eighty-seven thousand, nine hundred seventy-eight".