321000721 has 2 divisors, whose sum is σ = 321000722. Its totient is φ = 321000720.

The previous prime is 321000709. The next prime is 321000733. The reversal of 321000721 is 127000123.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (321000709) and next prime (321000733).

It can be written as a sum of positive squares in only one way, i.e., 301508496 + 19492225 = 17364^2 + 4415^2 .

It is a cyclic number.

It is not a de Polignac number, because 321000721 - 2⁵ = 321000689 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 321000695 and 321000704.

It is not a weakly prime, because it can be changed into another prime (321000791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160500360 + 160500361.

It is an arithmetic number, because the mean of its divisors is an integer number (160500361).

Almost surely, 2^321000721 is an apocalyptic number.

It is an amenable number.

321000721 is a deficient number, since it is larger than the sum of its proper divisors (1).

321000721 is an equidigital number, since it uses as much as digits as its factorization.

321000721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 84, while the sum is 16.

The square root of 321000721 is about 17916.4929883055. The cubic root of 321000721 is about 684.7026403947.

Adding to 321000721 its reverse (127000123), we get a palindrome (448000844).

The spelling of 321000721 in words is "three hundred twenty-one million, seven hundred twenty-one", and thus it is an aban number.