642643 has 4 divisors (see below), whose sum is σ = 670608. Its totient is φ = 614680.

The previous prime is 642623. The next prime is 642673. The reversal of 642643 is 346246.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-642643 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (642613) 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 3 ways as a sum of consecutive naturals, for example, 13948 + ... + 13993.

It is an arithmetic number, because the mean of its divisors is an integer number (167652).

2⁶⁴²⁶⁴³ is an apocalyptic number.

642643 is the 429-th centered heptagonal number.

642643 is a deficient number, since it is larger than the sum of its proper divisors (27965).

642643 is a wasteful number, since it uses less digits than its factorization.

642643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27964.

The product of its digits is 3456, while the sum is 25.

The square root of 642643 is about 801.6501730805. The cubic root of 642643 is about 86.2958532354.

Adding to 642643 its reverse (346246), we get a palindrome (988889).

The spelling of 642643 in words is "six hundred forty-two thousand, six hundred forty-three".