6661220756513 has 16 divisors (see below), whose sum is σ = 7091094067200. Its totient is φ = 6235584038400.

The previous prime is 6661220756459. The next prime is 6661220756569. The reversal of 6661220756513 is 3156570221666.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 6661220756513 - 2²⁶ = 6661153647649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6661220356513) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21016388 + ... + 21330986.

It is an arithmetic number, because the mean of its divisors is an integer number (443193379200).

Almost surely, 2^{6661220756513} is an apocalyptic number.

It is an amenable number.

6661220756513 is a deficient number, since it is larger than the sum of its proper divisors (429873310687).

6661220756513 is a wasteful number, since it uses less digits than its factorization.

6661220756513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321328.

The product of its (nonzero) digits is 2721600, while the sum is 50.

The spelling of 6661220756513 in words is "six trillion, six hundred sixty-one billion, two hundred twenty million, seven hundred fifty-six thousand, five hundred thirteen".