643865976 has 128 divisors (see below), whose sum is σ = 1934150400. Its totient is φ = 197285760.

The previous prime is 643865969. The next prime is 643865993. The reversal of 643865976 is 679568346.

643865976 is a `hidden beast` number, since 6 + 43 + 8 + 6 + 597 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1311091 + ... + 1311581.

It is an arithmetic number, because the mean of its divisors is an integer number (15110550).

Almost surely, 2^643865976 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 643865976, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (967075200).

643865976 is an abundant number, since it is smaller than the sum of its proper divisors (1290284424).

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

643865976 is a wasteful number, since it uses less digits than its factorization.

643865976 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 986 (or 976 counting only the distinct ones).

The product of its digits is 6531840, while the sum is 54.

The square root of 643865976 is about 25374.5143007704. The cubic root of 643865976 is about 863.5056006357.

The spelling of 643865976 in words is "six hundred forty-three million, eight hundred sixty-five thousand, nine hundred seventy-six".