640105 has 4 divisors (see below), whose sum is σ = 768132. Its totient is φ = 512080.

The previous prime is 640099. The next prime is 640109. The reversal of 640105 is 501046.

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 127449 + 512656 = 357^2 + 716^2 .

It is not a de Polignac number, because 640105 - 2¹³ = 631913 is a prime.

It is a super-2 number, since 2×640105² = 819468822050, which contains 22 as substring.

It is a Duffinian number.

640105 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (640109) 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, 64006 + ... + 64015.

It is an arithmetic number, because the mean of its divisors is an integer number (192033).

2⁶⁴⁰¹⁰⁵ is an apocalyptic number.

It is an amenable number.

640105 is a deficient number, since it is larger than the sum of its proper divisors (128027).

640105 is a wasteful number, since it uses less digits than its factorization.

640105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128026.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 640105 is about 800.0656223086. The cubic root of 640105 is about 86.1821001695.

The spelling of 640105 in words is "six hundred forty thousand, one hundred five".