321728993 has 2 divisors, whose sum is σ = 321728994. Its totient is φ = 321728992.

The previous prime is 321728923. The next prime is 321729011. The reversal of 321728993 is 399827123.

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., 320839744 + 889249 = 17912^2 + 943^2 .

It is a cyclic number.

It is not a de Polignac number, because 321728993 - 2²⁰ = 320680417 is a prime.

It is not a weakly prime, because it can be changed into another prime (321728923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160864496 + 160864497.

It is an arithmetic number, because the mean of its divisors is an integer number (160864497).

Almost surely, 2^321728993 is an apocalyptic number.

It is an amenable number.

321728993 is a deficient number, since it is larger than the sum of its proper divisors (1).

321728993 is an equidigital number, since it uses as much as digits as its factorization.

321728993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 163296, while the sum is 44.

The square root of 321728993 is about 17936.8055405638. The cubic root of 321728993 is about 685.2200568142.

The spelling of 321728993 in words is "three hundred twenty-one million, seven hundred twenty-eight thousand, nine hundred ninety-three".