121217665721 has 2 divisors, whose sum is σ = 121217665722. Its totient is φ = 121217665720.

The previous prime is 121217665669. The next prime is 121217665727. The reversal of 121217665721 is 127566712121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 120227934121 + 989731600 = 346739^2 + 31460^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-121217665721 is a prime.

It is not a weakly prime, because it can be changed into another prime (121217665727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 60608832860 + 60608832861.

It is an arithmetic number, because the mean of its divisors is an integer number (60608832861).

Almost surely, 2^121217665721 is an apocalyptic number.

It is an amenable number.

121217665721 is a deficient number, since it is larger than the sum of its proper divisors (1).

121217665721 is an equidigital number, since it uses as much as digits as its factorization.

121217665721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 70560, while the sum is 41.

The spelling of 121217665721 in words is "one hundred twenty-one billion, two hundred seventeen million, six hundred sixty-five thousand, seven hundred twenty-one".