6643991040 has 80 divisors (see below), whose sum is σ = 21240033408. Its totient is φ = 1771728896.

The previous prime is 6643991033. The next prime is 6643991047. The reversal of 6643991040 is 401993466.

It is an interprime number because it is at equal distance from previous prime (6643991033) and next prime (6643991047).

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 = 6643990983 and 6643991001.

It is not an unprimeable number, because it can be changed into a prime (6643991047) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 424872 + ... + 440231.

Almost surely, 2^6643991040 is an apocalyptic number.

6643991040 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

6643991040 is an abundant number, since it is smaller than the sum of its proper divisors (14596042368).

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

6643991040 is an equidigital number, since it uses as much as digits as its factorization.

6643991040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 865129 (or 865113 counting only the distinct ones).

The product of its (nonzero) digits is 139968, while the sum is 42.

The square root of 6643991040 is about 81510.6805271555. The cubic root of 6643991040 is about 1879.9357756844.

The spelling of 6643991040 in words is "six billion, six hundred forty-three million, nine hundred ninety-one thousand, forty".