721864686173 has 2 divisors, whose sum is σ = 721864686174. Its totient is φ = 721864686172.

The previous prime is 721864686143. The next prime is 721864686181. The reversal of 721864686173 is 371686468127.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 536734994884 + 185129691289 = 732622^2 + 430267^2 .

It is a cyclic number.

It is not a de Polignac number, because 721864686173 - 2¹⁴ = 721864669789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721864686143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360932343086 + 360932343087.

It is an arithmetic number, because the mean of its divisors is an integer number (360932343087).

Almost surely, 2^721864686173 is an apocalyptic number.

It is an amenable number.

721864686173 is a deficient number, since it is larger than the sum of its proper divisors (1).

721864686173 is an equidigital number, since it uses as much as digits as its factorization.

721864686173 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16257024, while the sum is 59.

The spelling of 721864686173 in words is "seven hundred twenty-one billion, eight hundred sixty-four million, six hundred eighty-six thousand, one hundred seventy-three".