721341209 has 2 divisors, whose sum is σ = 721341210. Its totient is φ = 721341208.

The previous prime is 721341199. The next prime is 721341223. The reversal of 721341209 is 902143127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 694849600 + 26491609 = 26360^2 + 5147^2 .

It is an emirp because it is prime and its reverse (902143127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 721341209 - 2⁴ = 721341193 is a prime.

It is not a weakly prime, because it can be changed into another prime (721341259) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360670604 + 360670605.

It is an arithmetic number, because the mean of its divisors is an integer number (360670605).

Almost surely, 2^721341209 is an apocalyptic number.

It is an amenable number.

721341209 is a deficient number, since it is larger than the sum of its proper divisors (1).

721341209 is an equidigital number, since it uses as much as digits as its factorization.

721341209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 721341209 is about 26857.7960562664. The cubic root of 721341209 is about 896.8371319166.

The spelling of 721341209 in words is "seven hundred twenty-one million, three hundred forty-one thousand, two hundred nine".