642009 has 4 divisors (see below), whose sum is σ = 856016. Its totient is φ = 428004.

The previous prime is 641981. The next prime is 642011. The reversal of 642009 is 900246.

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 not a de Polignac number, because 642009 - 2⁷ = 641881 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (642049) 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, 106999 + ... + 107004.

It is an arithmetic number, because the mean of its divisors is an integer number (214004).

2⁶⁴²⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

642009 is a deficient number, since it is larger than the sum of its proper divisors (214007).

642009 is a wasteful number, since it uses less digits than its factorization.

642009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214006.

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 642009 is about 801.2546411722. The cubic root of 642009 is about 86.2674654821.

The spelling of 642009 in words is "six hundred forty-two thousand, nine".