686557620 has 378 divisors, whose sum is σ = 2598325506. Its totient is φ = 151865280.

The previous prime is 686557591. The next prime is 686557621. The reversal of 686557620 is 26755686.

It can be written as a sum of positive squares in only one way, i.e., 549246096 + 137311524 = 23436^2 + 11718^2 .

It is a tau number, because it is divible by the number of its divisors (378).

It is a super-2 number, since 2×686557620² = 942722731160128800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (686557621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 125 ways as a sum of consecutive naturals, for example, 22147005 + ... + 22147035.

It is an arithmetic number, because the mean of its divisors is an integer number (6873877).

Almost surely, 2^686557620 is an apocalyptic number.

686557620 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 686557620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1299162753).

686557620 is an abundant number, since it is smaller than the sum of its proper divisors (1911767886).

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

686557620 is a wasteful number, since it uses less digits than its factorization.

686557620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103 (or 48 counting only the distinct ones).

The product of its (nonzero) digits is 604800, while the sum is 45.

The square root of 686557620 is about 26202.2445603425. The cubic root of 686557620 is about 882.1836352333.

Multiplying 686557620 by its sum of digits (45), we get a square (30895092900 = 175770²).

686557620 divided by its sum of digits (45) gives a square (15256836 = 3906²).

The spelling of 686557620 in words is "six hundred eighty-six million, five hundred fifty-seven thousand, six hundred twenty".