643825664 has 44 divisors (see below), whose sum is σ = 1291845324. Its totient is φ = 320864256.

The previous prime is 643825643. The next prime is 643825667. The reversal of 643825664 is 466528346.

It is a super-2 number, since 2×643825664² = 829022971250081792, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643825667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2096999 + ... + 2097305.

It is an arithmetic number, because the mean of its divisors is an integer number (29360121).

Almost surely, 2^643825664 is an apocalyptic number.

643825664 is a gapful number since it is divisible by the number (64) 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 643825664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (645922662).

643825664 is an abundant number, since it is smaller than the sum of its proper divisors (648019660).

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

643825664 is an frugal number, since it uses more digits than its factorization.

643825664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 349 (or 309 counting only the distinct ones).

The product of its digits is 829440, while the sum is 44.

The square root of 643825664 is about 25373.7199480092. The cubic root of 643825664 is about 863.4875790983.

The spelling of 643825664 in words is "six hundred forty-three million, eight hundred twenty-five thousand, six hundred sixty-four".