1221011121601 has 2 divisors, whose sum is σ = 1221011121602. Its totient is φ = 1221011121600.

The previous prime is 1221011121599. The next prime is 1221011121607. The reversal of 1221011121601 is 1061211101221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 955703715201 + 265307406400 = 977601^2 + 515080^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221011121601 - 2¹ = 1221011121599 is a prime.

Together with 1221011121599, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1221011121607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610505560800 + 610505560801.

It is an arithmetic number, because the mean of its divisors is an integer number (610505560801).

Almost surely, 2^{1221011121601} is an apocalyptic number.

It is an amenable number.

1221011121601 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221011121601 is an equidigital number, since it uses as much as digits as its factorization.

1221011121601 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48, while the sum is 19.

Adding to 1221011121601 its reverse (1061211101221), we get a palindrome (2282222222822).

The spelling of 1221011121601 in words is "one trillion, two hundred twenty-one billion, eleven million, one hundred twenty-one thousand, six hundred one".