6643853640 has 192 divisors, whose sum is σ = 23039976960. Its totient is φ = 1654548480.

The previous prime is 6643853639. The next prime is 6643853641. The reversal of 6643853640 is 463583466.

It is an interprime number because it is at equal distance from previous prime (6643853639) and next prime (6643853641).

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

It is not an unprimeable number, because it can be changed into a prime (6643853641) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 797577 + ... + 805863.

It is an arithmetic number, because the mean of its divisors is an integer number (119999880).

Almost surely, 2^6643853640 is an apocalyptic number.

6643853640 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 6643853640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (11519988480).

6643853640 is an abundant number, since it is smaller than the sum of its proper divisors (16396123320).

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

6643853640 is a wasteful number, since it uses less digits than its factorization.

6643853640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8452 (or 8445 counting only the distinct ones).

The product of its (nonzero) digits is 1244160, while the sum is 45.

The square root of 6643853640 is about 81509.8376884656. The cubic root of 6643853640 is about 1879.9228163574.

The spelling of 6643853640 in words is "six billion, six hundred forty-three million, eight hundred fifty-three thousand, six hundred forty".