642001 has 4 divisors (see below), whose sum is σ = 644004. Its totient is φ = 640000.

The previous prime is 641981. The next prime is 642011. The reversal of 642001 is 100246.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 100246 = 2 ⋅50123.

It can be written as a sum of positive squares in 2 ways, for example, as 638401 + 3600 = 799^2 + 60^2 .

It is a 3-Lehmer number, since φ(642001) divides (642001-1)³.

It is a cyclic number.

It is not a de Polignac number, because 642001 - 2⁵ = 641969 is a prime.

It is a Smith number, since the sum of its digits (13) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is a deceptive number, since it divides R₆₄₂₀₀₀.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (642011) 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, 400 + ... + 1201.

It is an arithmetic number, because the mean of its divisors is an integer number (161001).

It is a Poulet number, since it divides 2⁶⁴²⁰⁰⁰-1.

2⁶⁴²⁰⁰¹ is an apocalyptic number.

642001 is the 401-st decagonal number.

It is an amenable number.

642001 is a deficient number, since it is larger than the sum of its proper divisors (2003).

642001 is a wasteful number, since it uses less digits than its factorization.

642001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2002.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 642001 is about 801.2496489859. The cubic root of 642001 is about 86.2671071577.

Adding to 642001 its reverse (100246), we get a palindrome (742247).

The spelling of 642001 in words is "six hundred forty-two thousand, one".