684921257 has 2 divisors, whose sum is σ = 684921258. Its totient is φ = 684921256.

The previous prime is 684921227. The next prime is 684921269. The reversal of 684921257 is 752129486.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 684921241 + 16 = 26171^2 + 4^2 .

It is a cyclic number.

It is not a de Polignac number, because 684921257 - 2⁸ = 684921001 is a prime.

It is not a weakly prime, because it can be changed into another prime (684921227) 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 as a sum of consecutive naturals, namely, 342460628 + 342460629.

It is an arithmetic number, because the mean of its divisors is an integer number (342460629).

Almost surely, 2^684921257 is an apocalyptic number.

It is an amenable number.

684921257 is a deficient number, since it is larger than the sum of its proper divisors (1).

684921257 is an equidigital number, since it uses as much as digits as its factorization.

684921257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 241920, while the sum is 44.

The square root of 684921257 is about 26171.0003056819. Note that the first 3 decimals coincide. The cubic root of 684921257 is about 881.4822029357.

The spelling of 684921257 in words is "six hundred eighty-four million, nine hundred twenty-one thousand, two hundred fifty-seven".