31231121221 has 2 divisors, whose sum is σ = 31231121222. Its totient is φ = 31231121220.

The previous prime is 31231121197. The next prime is 31231121239. The reversal of 31231121221 is 12212113213.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 29109136996 + 2121984225 = 170614^2 + 46065^2 .

It is a cyclic number.

It is not a de Polignac number, because 31231121221 - 2¹¹ = 31231119173 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31231121281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15615560610 + 15615560611.

It is an arithmetic number, because the mean of its divisors is an integer number (15615560611).

Almost surely, 2^31231121221 is an apocalyptic number.

It is an amenable number.

31231121221 is a deficient number, since it is larger than the sum of its proper divisors (1).

31231121221 is an equidigital number, since it uses as much as digits as its factorization.

31231121221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 144, while the sum is 19.

Adding to 31231121221 its reverse (12212113213), we get a palindrome (43443234434).

The spelling of 31231121221 in words is "thirty-one billion, two hundred thirty-one million, one hundred twenty-one thousand, two hundred twenty-one".