640441468981 has 2 divisors, whose sum is σ = 640441468982. Its totient is φ = 640441468980.

The previous prime is 640441468949. The next prime is 640441468999. The reversal of 640441468981 is 189864144046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 325737298756 + 314704170225 = 570734^2 + 560985^2 .

It is a cyclic number.

It is not a de Polignac number, because 640441468981 - 2⁵ = 640441468949 is a prime.

It is a super-2 number, since 2×640441468981² (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 (640441468081) 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 as a sum of consecutive naturals, namely, 320220734490 + 320220734491.

It is an arithmetic number, because the mean of its divisors is an integer number (320220734491).

Almost surely, 2^640441468981 is an apocalyptic number.

It is an amenable number.

640441468981 is a deficient number, since it is larger than the sum of its proper divisors (1).

640441468981 is an equidigital number, since it uses as much as digits as its factorization.

640441468981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5308416, while the sum is 55.

The spelling of 640441468981 in words is "six hundred forty billion, four hundred forty-one million, four hundred sixty-eight thousand, nine hundred eighty-one".