643765 has 8 divisors (see below), whose sum is σ = 777600. Its totient is φ = 511632.

The previous prime is 643751. The next prime is 643781. The reversal of 643765 is 567346.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643765 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 672 + ... + 1318.

It is an arithmetic number, because the mean of its divisors is an integer number (97200).

2⁶⁴³⁷⁶⁵ is an apocalyptic number.

It is an amenable number.

643765 is a deficient number, since it is larger than the sum of its proper divisors (133835).

643765 is a wasteful number, since it uses less digits than its factorization.

643765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 851.

The product of its digits is 15120, while the sum is 31.

The square root of 643765 is about 802.3496743939. The cubic root of 643765 is about 86.3460457752.

The spelling of 643765 in words is "six hundred forty-three thousand, seven hundred sixty-five".