642409 has 4 divisors (see below), whose sum is σ = 676240. Its totient is φ = 608580.

The previous prime is 642407. The next prime is 642419. The reversal of 642409 is 904246.

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 642409 - 2¹ = 642407 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (642403) 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, 16887 + ... + 16924.

It is an arithmetic number, because the mean of its divisors is an integer number (169060).

2⁶⁴²⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

642409 is a deficient number, since it is larger than the sum of its proper divisors (33831).

642409 is a wasteful number, since it uses less digits than its factorization.

642409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33830.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 642409 is about 801.5042108436. The cubic root of 642409 is about 86.2853779113.

The spelling of 642409 in words is "six hundred forty-two thousand, four hundred nine".