66961395361 has 15 divisors (see below), whose sum is σ = 78131774643. Its totient is φ = 57384613440.

The previous prime is 66961395343. The next prime is 66961395367. The reversal of 66961395361 is 16359316966.

The square root of 66961395361 is 258769.

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., 8841828961 + 58119566400 = 94031^2 + 241080^2 .

It is not a de Polignac number, because 66961395361 - 2⁵ = 66961395329 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66961395367) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 12677041 + ... + 12682321.

Almost surely, 2^66961395361 is an apocalyptic number.

66961395361 is the 258769-th square number.

66961395361 is the 129385-th centered octagonal number.

It is an amenable number.

66961395361 is a deficient number, since it is larger than the sum of its proper divisors (11170379282).

66961395361 is an frugal number, since it uses more digits than its factorization.

66961395361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10590 (or 5288 counting only the distinct ones).

The product of its digits is 4723920, while the sum is 55.

The spelling of 66961395361 in words is "sixty-six billion, nine hundred sixty-one million, three hundred ninety-five thousand, three hundred sixty-one".