685439921 has 2 divisors, whose sum is σ = 685439922. Its totient is φ = 685439920.

The previous prime is 685439917. The next prime is 685439933. The reversal of 685439921 is 129934586.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 613800625 + 71639296 = 24775^2 + 8464^2 .

It is a cyclic number.

It is not a de Polignac number, because 685439921 - 2² = 685439917 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (685469921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342719960 + 342719961.

It is an arithmetic number, because the mean of its divisors is an integer number (342719961).

Almost surely, 2^685439921 is an apocalyptic number.

It is an amenable number.

685439921 is a deficient number, since it is larger than the sum of its proper divisors (1).

685439921 is an equidigital number, since it uses as much as digits as its factorization.

685439921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 466560, while the sum is 47.

The square root of 685439921 is about 26180.9075663927. The cubic root of 685439921 is about 881.7046507594.

The spelling of 685439921 in words is "six hundred eighty-five million, four hundred thirty-nine thousand, nine hundred twenty-one".