1213121023721 has 2 divisors, whose sum is σ = 1213121023722. Its totient is φ = 1213121023720.

The previous prime is 1213121023703. The next prime is 1213121023799. The reversal of 1213121023721 is 1273201213121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 948307863721 + 264813160000 = 973811^2 + 514600^2 .

It is a cyclic number.

It is not a de Polignac number, because 1213121023721 - 2³⁸ = 938243116777 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1213121026721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 606560511860 + 606560511861.

It is an arithmetic number, because the mean of its divisors is an integer number (606560511861).

Almost surely, 2^{1213121023721} is an apocalyptic number.

It is an amenable number.

1213121023721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1213121023721 is an equidigital number, since it uses as much as digits as its factorization.

1213121023721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 26.

Adding to 1213121023721 its reverse (1273201213121), we get a palindrome (2486322236842).

The spelling of 1213121023721 in words is "one trillion, two hundred thirteen billion, one hundred twenty-one million, twenty-three thousand, seven hundred twenty-one".