684840649 has 2 divisors, whose sum is σ = 684840650. Its totient is φ = 684840648.

The previous prime is 684840647. The next prime is 684840677. The reversal of 684840649 is 946048486.

It is a happy number.

684840649 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 428200249 + 256640400 = 20693^2 + 16020^2 .

It is a cyclic number.

It is not a de Polignac number, because 684840649 - 2¹ = 684840647 is a prime.

Together with 684840647, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (684840647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342420324 + 342420325.

It is an arithmetic number, because the mean of its divisors is an integer number (342420325).

Almost surely, 2^684840649 is an apocalyptic number.

It is an amenable number.

684840649 is a deficient number, since it is larger than the sum of its proper divisors (1).

684840649 is an equidigital number, since it uses as much as digits as its factorization.

684840649 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1327104, while the sum is 49.

The square root of 684840649 is about 26169.4602351673. The cubic root of 684840649 is about 881.4476211964.

The spelling of 684840649 in words is "six hundred eighty-four million, eight hundred forty thousand, six hundred forty-nine".