641663820 has 288 divisors, whose sum is σ = 2393664000. Its totient is φ = 138692736.

The previous prime is 641663809. The next prime is 641663837. The reversal of 641663820 is 28366146.

641663820 is a `hidden beast` number, since 6 + 4 + 16 + 638 + 2 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1172787 + ... + 1173333.

Almost surely, 2^641663820 is an apocalyptic number.

641663820 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 641663820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1196832000).

641663820 is an abundant number, since it is smaller than the sum of its proper divisors (1752000180).

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

641663820 is a wasteful number, since it uses less digits than its factorization.

641663820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 602 (or 583 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 641663820 is about 25331.0840668140. The cubic root of 641663820 is about 862.5200196991.

The spelling of 641663820 in words is "six hundred forty-one million, six hundred sixty-three thousand, eight hundred twenty".