• 642 can be written using four 4's:
642 is nontrivially palindromic in base 16.
642 is an esthetic number in base 12, because in such base its adjacent digits differ by 1.
It is a sphenic number, since it is the product of 3 distinct primes.
642 is an admirable number.
642 is an undulating number in base 16.
It is a straight-line number, since its digits are in arithmetic progression.
It is a plaindrome in base 12, base 14 and base 15.
It is a nialpdrome in base 10.
642 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
642 is a wasteful number, since it uses less digits than its factorization.
642 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 112.
The square root of 642 is about 25.3377189186. The cubic root of 642 is about 8.6267062367.
Subtracting from 642 its sum of digits (12), we obtain a triangular number (630 = T35).
Adding to 642 its reverse (246), we get a palindrome (888).
The spelling of 642 in words is "six hundred forty-two", and thus it is an aban number.