• 642 can be written using four 4's:

642 has 8 divisors (see below), whose sum is σ = 1296. Its totient is φ = 212.

The previous prime is 641. The next prime is 643. The reversal of 642 is 246.

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 an interprime number because it is at equal distance from previous prime (641) and next prime (643).

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.

It is not an unprimeable number, because it can be changed into a prime (641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (3) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 48 + ... + 59.

It is an arithmetic number, because the mean of its divisors is an integer number (162).

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.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (648).

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 product of its digits is 48, while the sum is 12.

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 = T_{35}).

Adding to 642 its reverse (246), we get a palindrome (888).

It can be divided in two parts, 64 and 2, that multiplied together give a 7-th power (128 = 2^{7}).

The spelling of 642 in words is "six hundred forty-two", and thus it is an aban number.

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