643976 has 16 divisors (see below), whose sum is σ = 1220940. Its totient is φ = 318400.

The previous prime is 643969. The next prime is 643991. The reversal of 643976 is 679346.

It can be written as a sum of positive squares in 2 ways, for example, as 592900 + 51076 = 770^2 + 226^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 410 + ... + 1206.

2⁶⁴³⁹⁷⁶ is an apocalyptic number.

It is an amenable number.

643976 is a deficient number, since it is larger than the sum of its proper divisors (576964).

643976 is a wasteful number, since it uses less digits than its factorization.

643976 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 904 (or 900 counting only the distinct ones).

The product of its digits is 27216, while the sum is 35.

The square root of 643976 is about 802.4811524266. The cubic root of 643976 is about 86.3554783195.

The spelling of 643976 in words is "six hundred forty-three thousand, nine hundred seventy-six".