731216221 has 2 divisors, whose sum is σ = 731216222. Its totient is φ = 731216220.

The previous prime is 731216219. The next prime is 731216231. The reversal of 731216221 is 122612137.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 594676996 + 136539225 = 24386^2 + 11685^2 .

It is an emirp because it is prime and its reverse (122612137) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 731216221 - 2¹ = 731216219 is a prime.

Together with 731216219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (731216201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 365608110 + 365608111.

It is an arithmetic number, because the mean of its divisors is an integer number (365608111).

Almost surely, 2^731216221 is an apocalyptic number.

It is an amenable number.

731216221 is a deficient number, since it is larger than the sum of its proper divisors (1).

731216221 is an equidigital number, since it uses as much as digits as its factorization.

731216221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1008, while the sum is 25.

The square root of 731216221 is about 27041.0099848360. The cubic root of 731216221 is about 900.9111024498.

Adding to 731216221 its reverse (122612137), we get a palindrome (853828358).

The spelling of 731216221 in words is "seven hundred thirty-one million, two hundred sixteen thousand, two hundred twenty-one".