643963 has 4 divisors (see below), whose sum is σ = 664768. Its totient is φ = 623160.

The previous prime is 643961. The next prime is 643969. The reversal of 643963 is 369346.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 643963 - 2¹ = 643961 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 20773 = 643963 / (6 + 4 + 3 + 9 + 6 + 3).

It is a d-powerful number, because it can be written as 6 + 4⁸ + 9² + 3⁵ + 6⁶ + 3¹² .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10356 + ... + 10417.

It is an arithmetic number, because the mean of its divisors is an integer number (166192).

2⁶⁴³⁹⁶³ is an apocalyptic number.

643963 is a deficient number, since it is larger than the sum of its proper divisors (20805).

643963 is a wasteful number, since it uses less digits than its factorization.

643963 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20804.

The product of its digits is 11664, while the sum is 31.

The square root of 643963 is about 802.4730525071. The cubic root of 643963 is about 86.3548972270.

The spelling of 643963 in words is "six hundred forty-three thousand, nine hundred sixty-three".