685400638 has 16 divisors (see below), whose sum is σ = 1142902656. Its totient is φ = 306133920.

The previous prime is 685400633. The next prime is 685400657. The reversal of 685400638 is 836004586.

685400638 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 685400638.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (685400633) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 424381 + ... + 425992.

It is an arithmetic number, because the mean of its divisors is an integer number (71431416).

Almost surely, 2^685400638 is an apocalyptic number.

685400638 is a deficient number, since it is larger than the sum of its proper divisors (457502018).

685400638 is a wasteful number, since it uses less digits than its factorization.

685400638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 850419.

The product of its (nonzero) digits is 138240, while the sum is 40.

The square root of 685400638 is about 26180.1573333699. The cubic root of 685400638 is about 881.6878067519.

The spelling of 685400638 in words is "six hundred eighty-five million, four hundred thousand, six hundred thirty-eight".