640513281 has 4 divisors (see below), whose sum is σ = 854017712. Its totient is φ = 427008852.

The previous prime is 640513249. The next prime is 640513421. The reversal of 640513281 is 182315046.

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 640513281 - 2⁵ = 640513249 is a prime.

It is a super-2 number, since 2×640513281² = 820514526274769922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (640513201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106752211 + ... + 106752216.

It is an arithmetic number, because the mean of its divisors is an integer number (213504428).

Almost surely, 2^640513281 is an apocalyptic number.

It is an amenable number.

640513281 is a deficient number, since it is larger than the sum of its proper divisors (213504431).

640513281 is a wasteful number, since it uses less digits than its factorization.

640513281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213504430.

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 640513281 is about 25308.3638546628. The cubic root of 640513281 is about 862.0041957831.

The spelling of 640513281 in words is "six hundred forty million, five hundred thirteen thousand, two hundred eighty-one".