31223067721 has 2 divisors, whose sum is σ = 31223067722. Its totient is φ = 31223067720.

The previous prime is 31223067691. The next prime is 31223067749. The reversal of 31223067721 is 12776032213.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 29687290000 + 1535777721 = 172300^2 + 39189^2 .

It is a cyclic number.

It is not a de Polignac number, because 31223067721 - 2¹³ = 31223059529 is a prime.

It is not a weakly prime, because it can be changed into another prime (31223067121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15611533860 + 15611533861.

It is an arithmetic number, because the mean of its divisors is an integer number (15611533861).

Almost surely, 2^31223067721 is an apocalyptic number.

It is an amenable number.

31223067721 is a deficient number, since it is larger than the sum of its proper divisors (1).

31223067721 is an equidigital number, since it uses as much as digits as its factorization.

31223067721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 21168, while the sum is 34.

Adding to 31223067721 its reverse (12776032213), we get a palindrome (43999099934).

The spelling of 31223067721 in words is "thirty-one billion, two hundred twenty-three million, sixty-seven thousand, seven hundred twenty-one".