6641568581621 has 4 divisors (see below), whose sum is σ = 6641724900000. Its totient is φ = 6641412263244.

The previous prime is 6641568581611. The next prime is 6641568581623. The reversal of 6641568581621 is 1261858651466.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6641568581621 is a prime.

It is a super-2 number, since 2×6641568581621² (a number of 26 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6641568581623) 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, 78095441 + ... + 78180438.

It is an arithmetic number, because the mean of its divisors is an integer number (1660431225000).

Almost surely, 2^{6641568581621} is an apocalyptic number.

It is an amenable number.

6641568581621 is a deficient number, since it is larger than the sum of its proper divisors (156318379).

6641568581621 is a wasteful number, since it uses less digits than its factorization.

6641568581621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156318378.

The product of its digits is 16588800, while the sum is 59.

The spelling of 6641568581621 in words is "six trillion, six hundred forty-one billion, five hundred sixty-eight million, five hundred eighty-one thousand, six hundred twenty-one".