640681340426 has 4 divisors (see below), whose sum is σ = 961022010642. Its totient is φ = 320340670212.

The previous prime is 640681340423. The next prime is 640681340471. The reversal of 640681340426 is 624043186046.

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

It can be written as a sum of positive squares in only one way, i.e., 402926605225 + 237754735201 = 634765^2 + 487601^2 .

It is a super-2 number, since 2×640681340426² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (640681340423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160170335105 + ... + 160170335108.

Almost surely, 2^640681340426 is an apocalyptic number.

640681340426 is a deficient number, since it is larger than the sum of its proper divisors (320340670216).

640681340426 is a wasteful number, since it uses less digits than its factorization.

640681340426 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320340670215.

The product of its (nonzero) digits is 663552, while the sum is 44.

The spelling of 640681340426 in words is "six hundred forty billion, six hundred eighty-one million, three hundred forty thousand, four hundred twenty-six".