664659738261 has 10 divisors (see below), whose sum is σ = 992886769622. Its totient is φ = 443106492120.

The previous prime is 664659738221. The next prime is 664659738277. The reversal of 664659738261 is 162837956466.

664659738261 is a `hidden beast` number, since 6 + 6 + 4 + 6 + 597 + 38 + 2 + 6 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 508520167236 + 156139571025 = 713106^2 + 395145^2 .

It is not a de Polignac number, because 664659738261 - 2¹³ = 664659730069 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664659738221) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 4102837810 + ... + 4102837971.

Almost surely, 2^664659738261 is an apocalyptic number.

It is an amenable number.

664659738261 is a deficient number, since it is larger than the sum of its proper divisors (328227031361).

664659738261 is an equidigital number, since it uses as much as digits as its factorization.

664659738261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8205675793 (or 8205675784 counting only the distinct ones).

The product of its digits is 78382080, while the sum is 63.

The spelling of 664659738261 in words is "six hundred sixty-four billion, six hundred fifty-nine million, seven hundred thirty-eight thousand, two hundred sixty-one".