640248376681 has 2 divisors, whose sum is σ = 640248376682. Its totient is φ = 640248376680.

The previous prime is 640248376673. The next prime is 640248376687. The reversal of 640248376681 is 186673842046.

It is a happy number.

640248376681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 529815117456 + 110433259225 = 727884^2 + 332315^2 .

It is a cyclic number.

It is not a de Polignac number, because 640248376681 - 2³ = 640248376673 is a prime.

It is a super-2 number, since 2×640248376681² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (640248376687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320124188340 + 320124188341.

It is an arithmetic number, because the mean of its divisors is an integer number (320124188341).

Almost surely, 2^640248376681 is an apocalyptic number.

It is an amenable number.

640248376681 is a deficient number, since it is larger than the sum of its proper divisors (1).

640248376681 is an equidigital number, since it uses as much as digits as its factorization.

640248376681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9289728, while the sum is 55.

The spelling of 640248376681 in words is "six hundred forty billion, two hundred forty-eight million, three hundred seventy-six thousand, six hundred eighty-one".