6640870780465 has 4 divisors (see below), whose sum is σ = 7969044936564. Its totient is φ = 5312696624368.

The previous prime is 6640870780399. The next prime is 6640870780469. The reversal of 6640870780465 is 5640870780466.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 4660456298481 + 1980414481984 = 2158809^2 + 1407272^2 .

It is a cyclic number.

It is not a de Polignac number, because 6640870780465 - 2²³ = 6640862391857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6640870780469) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 664087078042 + ... + 664087078051.

It is an arithmetic number, because the mean of its divisors is an integer number (1992261234141).

Almost surely, 2^{6640870780465} is an apocalyptic number.

It is an amenable number.

6640870780465 is a deficient number, since it is larger than the sum of its proper divisors (1328174156099).

6640870780465 is a wasteful number, since it uses less digits than its factorization.

6640870780465 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1328174156098.

The product of its (nonzero) digits is 54190080, while the sum is 61.

Subtracting from 6640870780465 its reverse (5640870780466), we obtain a palindrome (999999999999).

The spelling of 6640870780465 in words is "six trillion, six hundred forty billion, eight hundred seventy million, seven hundred eighty thousand, four hundred sixty-five".