642221 has 4 divisors (see below), whose sum is σ = 643932. Its totient is φ = 640512.

The previous prime is 642217. The next prime is 642223. The reversal of 642221 is 122246.

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

It can be written as a sum of positive squares in 2 ways, for example, as 265225 + 376996 = 515^2 + 614^2 .

It is a cyclic number.

It is not a de Polignac number, because 642221 - 2² = 642217 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 642221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642223) 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, 20 + ... + 1133.

It is an arithmetic number, because the mean of its divisors is an integer number (160983).

2⁶⁴²²²¹ is an apocalyptic number.

It is an amenable number.

642221 is a deficient number, since it is larger than the sum of its proper divisors (1711).

642221 is a wasteful number, since it uses less digits than its factorization.

642221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1710.

The product of its digits is 192, while the sum is 17.

The square root of 642221 is about 801.3869227783. The cubic root of 642221 is about 86.2769599960.

Adding to 642221 its reverse (122246), we get a palindrome (764467).

The spelling of 642221 in words is "six hundred forty-two thousand, two hundred twenty-one".