685021321 has 2 divisors, whose sum is σ = 685021322. Its totient is φ = 685021320.

The previous prime is 685021319. The next prime is 685021349. The reversal of 685021321 is 123120586.

It is an a-pointer prime, because the next prime (685021349) can be obtained adding 685021321 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 603390096 + 81631225 = 24564^2 + 9035^2 .

It is a cyclic number.

It is not a de Polignac number, because 685021321 - 2¹ = 685021319 is a prime.

Together with 685021319, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 685021321.

It is not a weakly prime, because it can be changed into another prime (685021021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342510660 + 342510661.

It is an arithmetic number, because the mean of its divisors is an integer number (342510661).

Almost surely, 2^685021321 is an apocalyptic number.

It is an amenable number.

685021321 is a deficient number, since it is larger than the sum of its proper divisors (1).

685021321 is an equidigital number, since it uses as much as digits as its factorization.

685021321 is an evil number, because the sum of its binary digits is even.

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

The square root of 685021321 is about 26172.9119702031. The cubic root of 685021321 is about 881.5251277436.

The spelling of 685021321 in words is "six hundred eighty-five million, twenty-one thousand, three hundred twenty-one".