678781 has 4 divisors (see below), whose sum is σ = 682492. Its totient is φ = 675072.

The previous prime is 678779. The next prime is 678809. The reversal of 678781 is 187876.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 443556 + 235225 = 666^2 + 485^2 .

It is a cyclic number.

It is not a de Polignac number, because 678781 - 2¹ = 678779 is a prime.

It is a super-2 number, since 2×678781² = 921487291922, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 678781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (678721) 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 3 ways as a sum of consecutive naturals, for example, 1566 + ... + 1951.

It is an arithmetic number, because the mean of its divisors is an integer number (170623).

2⁶⁷⁸⁷⁸¹ is an apocalyptic number.

It is an amenable number.

678781 is a deficient number, since it is larger than the sum of its proper divisors (3711).

678781 is a wasteful number, since it uses less digits than its factorization.

678781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3710.

The product of its digits is 18816, while the sum is 37.

The square root of 678781 is about 823.8816662604. The cubic root of 678781 is about 87.8840155876.

It can be divided in two parts, 6 and 78781, that added together give a palindrome (78787).

The spelling of 678781 in words is "six hundred seventy-eight thousand, seven hundred eighty-one".