643663 has 6 divisors (see below), whose sum is σ = 679704. Its totient is φ = 609444.

The previous prime is 643661. The next prime is 643681. The reversal of 643663 is 366346.

It is not a de Polignac number, because 643663 - 2¹ = 643661 is a prime.

It is an Ulam number.

It is a Duffinian number.

643663 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643661) by changing a digit.

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 5 ways as a sum of consecutive naturals, for example, 531 + ... + 1252.

It is an arithmetic number, because the mean of its divisors is an integer number (113284).

2⁶⁴³⁶⁶³ is an apocalyptic number.

643663 is a deficient number, since it is larger than the sum of its proper divisors (36041).

643663 is a wasteful number, since it uses less digits than its factorization.

643663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1821 (or 1802 counting only the distinct ones).

The product of its digits is 7776, while the sum is 28.

The square root of 643663 is about 802.2861085673. The cubic root of 643663 is about 86.3414852281.

It can be divided in two parts, 64 and 3663, that multiplied together give a palindrome (234432).

The spelling of 643663 in words is "six hundred forty-three thousand, six hundred sixty-three".