641663440 has 80 divisors (see below), whose sum is σ = 1713193920. Its totient is φ = 221045760.

The previous prime is 641663437. The next prime is 641663441. The reversal of 641663440 is 44366146.

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 = 641663396 and 641663405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (641663441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2469 + ... + 35908.

It is an arithmetic number, because the mean of its divisors is an integer number (21414924).

Almost surely, 2^641663440 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 641663440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (856596960).

641663440 is an abundant number, since it is smaller than the sum of its proper divisors (1071530480).

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

641663440 is a wasteful number, since it uses less digits than its factorization.

641663440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38420 (or 38414 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 34.

The square root of 641663440 is about 25331.0765661470. The cubic root of 641663440 is about 862.5198494347.

The spelling of 641663440 in words is "six hundred forty-one million, six hundred sixty-three thousand, four hundred forty".