640122643 has 4 divisors (see below), whose sum is σ = 647835048. Its totient is φ = 632410240.

The previous prime is 640122631. The next prime is 640122647. The reversal of 640122643 is 346221046.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 640122643 - 2¹³ = 640114451 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640122647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3856078 + ... + 3856243.

It is an arithmetic number, because the mean of its divisors is an integer number (161958762).

Almost surely, 2^640122643 is an apocalyptic number.

640122643 is a deficient number, since it is larger than the sum of its proper divisors (7712405).

640122643 is an equidigital number, since it uses as much as digits as its factorization.

640122643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7712404.

The product of its (nonzero) digits is 6912, while the sum is 28.

The square root of 640122643 is about 25300.6451103524. The cubic root of 640122643 is about 861.8289196498.

Adding to 640122643 its reverse (346221046), we get a palindrome (986343689).

The spelling of 640122643 in words is "six hundred forty million, one hundred twenty-two thousand, six hundred forty-three".