65726721661 has 2 divisors, whose sum is σ = 65726721662. Its totient is φ = 65726721660.

The previous prime is 65726721617. The next prime is 65726721667. The reversal of 65726721661 is 16612762756.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 65623068900 + 103652761 = 256170^2 + 10181^2 .

It is a cyclic number.

It is not a de Polignac number, because 65726721661 - 2¹³ = 65726713469 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (65726721667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32863360830 + 32863360831.

It is an arithmetic number, because the mean of its divisors is an integer number (32863360831).

Almost surely, 2^65726721661 is an apocalyptic number.

It is an amenable number.

65726721661 is a deficient number, since it is larger than the sum of its proper divisors (1).

65726721661 is an equidigital number, since it uses as much as digits as its factorization.

65726721661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1270080, while the sum is 49.

The spelling of 65726721661 in words is "sixty-five billion, seven hundred twenty-six million, seven hundred twenty-one thousand, six hundred sixty-one".