66173271721 has 2 divisors, whose sum is σ = 66173271722. Its totient is φ = 66173271720.

The previous prime is 66173271709. The next prime is 66173271751. The reversal of 66173271721 is 12717237166.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 38362706496 + 27810565225 = 195864^2 + 166765^2 .

It is a cyclic number.

It is not a de Polignac number, because 66173271721 - 2²⁵ = 66139717289 is a prime.

It is a super-2 number, since 2×66173271721² (a number of 22 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (66173271701) 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, 33086635860 + 33086635861.

It is an arithmetic number, because the mean of its divisors is an integer number (33086635861).

Almost surely, 2^66173271721 is an apocalyptic number.

It is an amenable number.

66173271721 is a deficient number, since it is larger than the sum of its proper divisors (1).

66173271721 is an equidigital number, since it uses as much as digits as its factorization.

66173271721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 148176, while the sum is 43.

The spelling of 66173271721 in words is "sixty-six billion, one hundred seventy-three million, two hundred seventy-one thousand, seven hundred twenty-one".