665902640 has 80 divisors (see below), whose sum is σ = 1724889600. Its totient is φ = 237382656.

The previous prime is 665902603. The next prime is 665902649. The reversal of 665902640 is 46209566.

665902640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 665902594 and 665902603.

It is not an unprimeable number, because it can be changed into a prime (665902649) 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, 19121 + ... + 41199.

It is an arithmetic number, because the mean of its divisors is an integer number (21561120).

Almost surely, 2^665902640 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 665902640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (862444800).

665902640 is an abundant number, since it is smaller than the sum of its proper divisors (1058986960).

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

665902640 is a wasteful number, since it uses less digits than its factorization.

665902640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22134 (or 22128 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 38.

The square root of 665902640 is about 25805.0894205000. The cubic root of 665902640 is about 873.2466177845.

The spelling of 665902640 in words is "six hundred sixty-five million, nine hundred two thousand, six hundred forty".