665556840 has 192 divisors, whose sum is σ = 2363437440. Its totient is φ = 161441280.

The previous prime is 665556839. The next prime is 665556869. The reversal of 665556840 is 48655566.

It is a happy number.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 331279 + ... + 333281.

It is an arithmetic number, because the mean of its divisors is an integer number (12309570).

Almost surely, 2^665556840 is an apocalyptic number.

665556840 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 665556840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1181718720).

665556840 is an abundant number, since it is smaller than the sum of its proper divisors (1697880600).

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

665556840 is a wasteful number, since it uses less digits than its factorization.

665556840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2104 (or 2097 counting only the distinct ones).

The product of its (nonzero) digits is 864000, while the sum is 45.

The square root of 665556840 is about 25798.3883217537. The cubic root of 665556840 is about 873.0954340390.

The spelling of 665556840 in words is "six hundred sixty-five million, five hundred fifty-six thousand, eight hundred forty".