678649 has 2 divisors, whose sum is σ = 678650. Its totient is φ = 678648.

The previous prime is 678647. The next prime is 678653. The reversal of 678649 is 946876.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 435600 + 243049 = 660^2 + 493^2 .

It is a cyclic number.

It is not a de Polignac number, because 678649 - 2¹ = 678647 is a prime.

Together with 678647, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (678641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 339324 + 339325.

It is an arithmetic number, because the mean of its divisors is an integer number (339325).

2⁶⁷⁸⁶⁴⁹ is an apocalyptic number.

It is an amenable number.

678649 is a deficient number, since it is larger than the sum of its proper divisors (1).

678649 is an equidigital number, since it uses as much as digits as its factorization.

678649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 40.

The square root of 678649 is about 823.8015537737. The cubic root of 678649 is about 87.8783183931.

The spelling of 678649 in words is "six hundred seventy-eight thousand, six hundred forty-nine".