642021 has 4 divisors (see below), whose sum is σ = 856032. Its totient is φ = 428012.

The previous prime is 642013. The next prime is 642049. The reversal of 642021 is 120246.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 642021 - 2³ = 642013 is a prime.

It is a D-number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642011) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107001 + ... + 107006.

It is an arithmetic number, because the mean of its divisors is an integer number (214008).

2⁶⁴²⁰²¹ is an apocalyptic number.

It is an amenable number.

642021 is a deficient number, since it is larger than the sum of its proper divisors (214011).

642021 is a wasteful number, since it uses less digits than its factorization.

642021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214010.

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 642021 is about 801.2621293934. The cubic root of 642021 is about 86.2680029633.

Adding to 642021 its reverse (120246), we get a palindrome (762267).

It can be divided in two parts, 6420 and 21, that added together give a triangular number (6441 = T₁₁₃).

The spelling of 642021 in words is "six hundred forty-two thousand, twenty-one".