685223821 has 2 divisors, whose sum is σ = 685223822. Its totient is φ = 685223820.

The previous prime is 685223761. The next prime is 685223837. The reversal of 685223821 is 128322586.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 573075721 + 112148100 = 23939^2 + 10590^2 .

It is a cyclic number.

It is not a de Polignac number, because 685223821 - 2²¹ = 683126669 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (685223321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342611910 + 342611911.

It is an arithmetic number, because the mean of its divisors is an integer number (342611911).

Almost surely, 2^685223821 is an apocalyptic number.

It is an amenable number.

685223821 is a deficient number, since it is larger than the sum of its proper divisors (1).

685223821 is an equidigital number, since it uses as much as digits as its factorization.

685223821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46080, while the sum is 37.

The square root of 685223821 is about 26176.7801877924. The cubic root of 685223821 is about 881.6119820969.

The spelling of 685223821 in words is "six hundred eighty-five million, two hundred twenty-three thousand, eight hundred twenty-one".