643534956 has 84 divisors (see below), whose sum is σ = 1698522000. Its totient is φ = 213241248.

The previous prime is 643534919. The next prime is 643534967. The reversal of 643534956 is 659435346.

643534956 is a `hidden beast` number, since 64 + 3 + 534 + 9 + 56 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 579730 + ... + 580838.

It is an arithmetic number, because the mean of its divisors is an integer number (20220500).

Almost surely, 2^643534956 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 643534956, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (849261000).

643534956 is an abundant number, since it is smaller than the sum of its proper divisors (1054987044).

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

643534956 is a wasteful number, since it uses less digits than its factorization.

643534956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1330 (or 1313 counting only the distinct ones).

The product of its digits is 1166400, while the sum is 45.

The square root of 643534956 is about 25367.9907757788. The cubic root of 643534956 is about 863.3575953919.

The spelling of 643534956 in words is "six hundred forty-three million, five hundred thirty-four thousand, nine hundred fifty-six".