643407264 has 72 divisors (see below), whose sum is σ = 1846877760. Its totient is φ = 212454528.

The previous prime is 643407251. The next prime is 643407277. The reversal of 643407264 is 462704346.

643407264 is a `hidden beast` number, since 643 + 4 + 0 + 7 + 2 + 6 + 4 = 666.

It is an interprime number because it is at equal distance from previous prime (643407251) and next prime (643407277).

It is a tau number, because it is divible by the number of its divisors (72).

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 11 ways as a sum of consecutive naturals, for example, 20377 + ... + 41255.

It is an arithmetic number, because the mean of its divisors is an integer number (25651080).

Almost surely, 2^643407264 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 643407264, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (923438880).

643407264 is an abundant number, since it is smaller than the sum of its proper divisors (1203470496).

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

643407264 is a wasteful number, since it uses less digits than its factorization.

643407264 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21002 (or 20991 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 36.

The square root of 643407264 is about 25365.4738571942. The cubic root of 643407264 is about 863.3004883410.

The spelling of 643407264 in words is "six hundred forty-three million, four hundred seven thousand, two hundred sixty-four".