640043358781 has 2 divisors, whose sum is σ = 640043358782. Its totient is φ = 640043358780.

The previous prime is 640043358767. The next prime is 640043358803. The reversal of 640043358781 is 187853340046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 510953336100 + 129090022681 = 714810^2 + 359291^2 .

It is a cyclic number.

It is not a de Polignac number, because 640043358781 - 2²³ = 640034970173 is a prime.

It is a super-2 number, since 2×640043358781² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640043358881) 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, 320021679390 + 320021679391.

It is an arithmetic number, because the mean of its divisors is an integer number (320021679391).

Almost surely, 2^640043358781 is an apocalyptic number.

It is an amenable number.

640043358781 is a deficient number, since it is larger than the sum of its proper divisors (1).

640043358781 is an equidigital number, since it uses as much as digits as its factorization.

640043358781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1935360, while the sum is 49.

The spelling of 640043358781 in words is "six hundred forty billion, forty-three million, three hundred fifty-eight thousand, seven hundred eighty-one".