640005081 has 4 divisors (see below), whose sum is σ = 853340112. Its totient is φ = 426670052.

The previous prime is 640005073. The next prime is 640005097. The reversal of 640005081 is 180500046.

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 640005081 - 2³ = 640005073 is a prime.

It is a super-2 number, since 2×640005081² = 819213007411633122, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (640005011) 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, 106667511 + ... + 106667516.

It is an arithmetic number, because the mean of its divisors is an integer number (213335028).

Almost surely, 2^640005081 is an apocalyptic number.

It is an amenable number.

640005081 is a deficient number, since it is larger than the sum of its proper divisors (213335031).

640005081 is a wasteful number, since it uses less digits than its factorization.

640005081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213335030.

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 640005081 is about 25298.3217032277. The cubic root of 640005081 is about 861.7761565656.

The spelling of 640005081 in words is "six hundred forty million, five thousand, eighty-one".