1211209999721 has 2 divisors, whose sum is σ = 1211209999722. Its totient is φ = 1211209999720.

The previous prime is 1211209999709. The next prime is 1211209999733. The reversal of 1211209999721 is 1279999021121.

It is a balanced prime because it is at equal distance from previous prime (1211209999709) and next prime (1211209999733).

It can be written as a sum of positive squares in only one way, i.e., 1178136576400 + 33073423321 = 1085420^2 + 181861^2 .

It is a cyclic number.

It is not a de Polignac number, because 1211209999721 - 2¹⁴ = 1211209983337 is a prime.

It is not a weakly prime, because it can be changed into another prime (1211209999921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 605604999860 + 605604999861.

It is an arithmetic number, because the mean of its divisors is an integer number (605604999861).

Almost surely, 2^{1211209999721} is an apocalyptic number.

It is an amenable number.

1211209999721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1211209999721 is an equidigital number, since it uses as much as digits as its factorization.

1211209999721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 367416, while the sum is 53.

The spelling of 1211209999721 in words is "one trillion, two hundred eleven billion, two hundred nine million, nine hundred ninety-nine thousand, seven hundred twenty-one".