6720661557 has 16 divisors (see below), whose sum is σ = 9963290880. Its totient is φ = 4477401216.

The previous prime is 6720661529. The next prime is 6720661559. The reversal of 6720661557 is 7551660276.

6720661557 is a `hidden beast` number, since 6 + 7 + 20 + 6 + 615 + 5 + 7 = 666.

It is not a de Polignac number, because 6720661557 - 2¹⁹ = 6720137269 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6720661559) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43548 + ... + 123845.

It is an arithmetic number, because the mean of its divisors is an integer number (622705680).

Almost surely, 2^6720661557 is an apocalyptic number.

It is an amenable number.

6720661557 is a deficient number, since it is larger than the sum of its proper divisors (3242629323).

6720661557 is a wasteful number, since it uses less digits than its factorization.

6720661557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168889 (or 168883 counting only the distinct ones).

The product of its (nonzero) digits is 529200, while the sum is 45.

The square root of 6720661557 is about 81979.6411129007. The cubic root of 6720661557 is about 1887.1395151636.

The spelling of 6720661557 in words is "six billion, seven hundred twenty million, six hundred sixty-one thousand, five hundred fifty-seven".