641555840 has 64 divisors (see below), whose sum is σ = 1553256000. Its totient is φ = 253353984.

The previous prime is 641555807. The next prime is 641555879. The reversal of 641555840 is 48555146.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (64).

It is a junction number, because it is equal to n+sod(n) for n = 641555794 and 641555803.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44216 + ... + 56904.

It is an arithmetic number, because the mean of its divisors is an integer number (24269625).

Almost surely, 2^641555840 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 641555840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (776628000).

641555840 is an abundant number, since it is smaller than the sum of its proper divisors (911700160).

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

641555840 is a wasteful number, since it uses less digits than its factorization.

641555840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12787 (or 12775 counting only the distinct ones).

The product of its (nonzero) digits is 96000, while the sum is 38.

The square root of 641555840 is about 25328.9526036905. The cubic root of 641555840 is about 862.4716349980.

The spelling of 641555840 in words is "six hundred forty-one million, five hundred fifty-five thousand, eight hundred forty".