642666 has 16 divisors (see below), whose sum is σ = 1341504. Its totient is φ = 204864.

The previous prime is 642623. The next prime is 642673. The reversal of 642666 is 666246.

642666 is a modest number, since divided by 666 gives 642 as remainder.

It is a congruent number.

It is an unprimeable number.

642666 is an untouchable number, because it is not equal to the sum of proper divisors of any 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, 2191 + ... + 2466.

It is an arithmetic number, because the mean of its divisors is an integer number (83844).

2⁶⁴²⁶⁶⁶ is an apocalyptic number.

642666 is an abundant number, since it is smaller than the sum of its proper divisors (698838).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

642666 is a wasteful number, since it uses less digits than its factorization.

642666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4685.

The product of its digits is 10368, while the sum is 30.

The square root of 642666 is about 801.6645183616. The cubic root of 642666 is about 86.2968827240.

The spelling of 642666 in words is "six hundred forty-two thousand, six hundred sixty-six".