641971540 has 72 divisors (see below), whose sum is σ = 1573576200. Its totient is φ = 219356928.

The previous prime is 641971537. The next prime is 641971549. The reversal of 641971540 is 45179146.

It can be written as a sum of positive squares in 4 ways, for example, as 151437636 + 490533904 = 12306^2 + 22148^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 641971540.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (641971549) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 341082 + ... + 342958.

It is an arithmetic number, because the mean of its divisors is an integer number (21855225).

Almost surely, 2^641971540 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 641971540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (786788100).

641971540 is an abundant number, since it is smaller than the sum of its proper divisors (931604660).

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

641971540 is a wasteful number, since it uses less digits than its factorization.

641971540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2249 (or 2240 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 37.

The square root of 641971540 is about 25337.1572991131. The cubic root of 641971540 is about 862.6578760218.

The spelling of 641971540 in words is "six hundred forty-one million, nine hundred seventy-one thousand, five hundred forty".