66557320 has 64 divisors (see below), whose sum is σ = 156265200. Its totient is φ = 25482240.

The previous prime is 66557303. The next prime is 66557321. The reversal of 66557320 is 2375566.

It can be written as a sum of positive squares in 8 ways, for example, as 850084 + 65707236 = 922^2 + 8106^2 .

It is not an unprimeable number, because it can be changed into a prime (66557321) 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, 209802 + ... + 210118.

Almost surely, 2^66557320 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 66557320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (78132600).

66557320 is an abundant number, since it is smaller than the sum of its proper divisors (89707880).

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

66557320 is a wasteful number, since it uses less digits than its factorization.

66557320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 538 (or 534 counting only the distinct ones).

The product of its (nonzero) digits is 37800, while the sum is 34.

The square root of 66557320 is about 8158.2669728319. The cubic root of 66557320 is about 405.2583222179.

The spelling of 66557320 in words is "sixty-six million, five hundred fifty-seven thousand, three hundred twenty".