642638 has 4 divisors (see below), whose sum is σ = 963960. Its totient is φ = 321318.

The previous prime is 642623. The next prime is 642673. The reversal of 642638 is 836246.

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

It is a self number, because there is not a number n which added to its sum of digits gives 642638.

It is a congruent number.

It is an unprimeable number.

642638 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 as a sum of consecutive naturals, namely, 160658 + ... + 160661.

It is an arithmetic number, because the mean of its divisors is an integer number (240990).

2⁶⁴²⁶³⁸ is an apocalyptic number.

642638 is a deficient number, since it is larger than the sum of its proper divisors (321322).

642638 is a wasteful number, since it uses less digits than its factorization.

642638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 321321.

The product of its digits is 6912, while the sum is 29.

The square root of 642638 is about 801.6470545072. The cubic root of 642638 is about 86.2956294303.

The spelling of 642638 in words is "six hundred forty-two thousand, six hundred thirty-eight".