643912 has 8 divisors (see below), whose sum is σ = 1207350. Its totient is φ = 321952.

The previous prime is 643889. The next prime is 643919. The reversal of 643912 is 219346.

It can be written as a sum of positive squares in only one way, i.e., 367236 + 276676 = 606^2 + 526^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (643919) by changing a digit.

643912 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40237 + ... + 40252.

2⁶⁴³⁹¹² is an apocalyptic number.

It is an amenable number.

643912 is a deficient number, since it is larger than the sum of its proper divisors (563438).

643912 is a wasteful number, since it uses less digits than its factorization.

643912 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80495 (or 80491 counting only the distinct ones).

The product of its digits is 1296, while the sum is 25.

The square root of 643912 is about 802.4412751099. The cubic root of 643912 is about 86.3526174811.

The spelling of 643912 in words is "six hundred forty-three thousand, nine hundred twelve".