721100221 has 2 divisors, whose sum is σ = 721100222. Its totient is φ = 721100220.

The previous prime is 721100189. The next prime is 721100227. The reversal of 721100221 is 122001127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 538472025 + 182628196 = 23205^2 + 13514^2 .

It is a cyclic number.

It is not a de Polignac number, because 721100221 - 2⁵ = 721100189 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 721100195 and 721100204.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721100227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360550110 + 360550111.

It is an arithmetic number, because the mean of its divisors is an integer number (360550111).

Almost surely, 2^721100221 is an apocalyptic number.

It is an amenable number.

721100221 is a deficient number, since it is larger than the sum of its proper divisors (1).

721100221 is an equidigital number, since it uses as much as digits as its factorization.

721100221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 56, while the sum is 16.

The square root of 721100221 is about 26853.3093118893. The cubic root of 721100221 is about 896.7372480444.

Adding to 721100221 its reverse (122001127), we get a palindrome (843101348).

The spelling of 721100221 in words is "seven hundred twenty-one million, one hundred thousand, two hundred twenty-one".