6642078391729 has 9 divisors (see below), whose sum is σ = 7300828071019. Its totient is φ = 6038227311160.

The previous prime is 6642078391679. The next prime is 6642078391789. The reversal of 6642078391729 is 9271938702466.

The square root of 6642078391729 is 2577223.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 1138606373025 + 5503472018704 = 1067055^2 + 2345948^2 .

It is not a de Polignac number, because 6642078391729 - 2⁷ = 6642078391601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6642078391789) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 28232307 + ... + 28466599.

Almost surely, 2^{6642078391729} is an apocalyptic number.

6642078391729 is the 2577223-rd square number.

6642078391729 is the 1288612-nd centered octagonal number.

It is an amenable number.

6642078391729 is a deficient number, since it is larger than the sum of its proper divisors (658749679290).

6642078391729 is an frugal number, since it uses more digits than its factorization.

6642078391729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 468608 (or 234304 counting only the distinct ones).

The product of its (nonzero) digits is 54867456, while the sum is 64.

Multiplying 6642078391729 by its sum of digits (64), we get a square (425093017070656 = 20617784²).

The spelling of 6642078391729 in words is "six trillion, six hundred forty-two billion, seventy-eight million, three hundred ninety-one thousand, seven hundred twenty-nine".