6645680640 has 320 divisors, whose sum is σ = 23917576320. Its totient is φ = 1770688512.

The previous prime is 6645680617. The next prime is 6645680683. The reversal of 6645680640 is 460865466.

6645680640 is a `hidden beast` number, since 66 + 456 + 80 + 64 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (320).

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

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5598127 + ... + 5599313.

It is an arithmetic number, because the mean of its divisors is an integer number (74742426).

Almost surely, 2^6645680640 is an apocalyptic number.

6645680640 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 6645680640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (11958788160).

6645680640 is an abundant number, since it is smaller than the sum of its proper divisors (17271895680).

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

6645680640 is an frugal number, since it uses more digits than its factorization.

6645680640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1231 (or 1197 counting only the distinct ones).

The product of its (nonzero) digits is 829440, while the sum is 45.

The square root of 6645680640 is about 81521.0441542550. The cubic root of 6645680640 is about 1880.0951211868.

The spelling of 6645680640 in words is "six billion, six hundred forty-five million, six hundred eighty thousand, six hundred forty".