685561820 has 48 divisors (see below), whose sum is σ = 1489295808. Its totient is φ = 264906240.

The previous prime is 685561817. The next prime is 685561829. The reversal of 685561820 is 28165586.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (685561829) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 80402 + ... + 88518.

It is an arithmetic number, because the mean of its divisors is an integer number (31026996).

Almost surely, 2^685561820 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 685561820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (744647904).

685561820 is an abundant number, since it is smaller than the sum of its proper divisors (803733988).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

685561820 is a wasteful number, since it uses less digits than its factorization.

685561820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8270 (or 8268 counting only the distinct ones).

The product of its (nonzero) digits is 115200, while the sum is 41.

The square root of 685561820 is about 26183.2354761592. The cubic root of 685561820 is about 881.7569152692.

The spelling of 685561820 in words is "six hundred eighty-five million, five hundred sixty-one thousand, eight hundred twenty".