685621 has 2 divisors, whose sum is σ = 685622. Its totient is φ = 685620.

The previous prime is 685613. The next prime is 685631. The reversal of 685621 is 126586.

685621 = 585² + 586².

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 343396 + 342225 = 586^2 + 585^2 .

It is a cyclic number.

It is not a de Polignac number, because 685621 - 2³ = 685613 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 685621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (685631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342810 + 342811.

It is an arithmetic number, because the mean of its divisors is an integer number (342811).

2⁶⁸⁵⁶²¹ is an apocalyptic number.

685621 is the 586-th centered square number.

It is an amenable number.

685621 is a deficient number, since it is larger than the sum of its proper divisors (1).

685621 is an equidigital number, since it uses as much as digits as its factorization.

685621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2880, while the sum is 28.

The square root of 685621 is about 828.0223426937. The cubic root of 685621 is about 88.1782286613.

The spelling of 685621 in words is "six hundred eighty-five thousand, six hundred twenty-one".