1221010721161 has 16 divisors (see below), whose sum is σ = 1537371358848. Its totient is φ = 942016752000.

The previous prime is 1221010721149. The next prime is 1221010721167. The reversal of 1221010721161 is 1611270101221.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1221010721161 - 2⁵ = 1221010721129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221010721167) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 78493620 + ... + 78509173.

It is an arithmetic number, because the mean of its divisors is an integer number (96085709928).

Almost surely, 2^{1221010721161} is an apocalyptic number.

1221010721161 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221010721161 is a deficient number, since it is larger than the sum of its proper divisors (316360637687).

1221010721161 is a wasteful number, since it uses less digits than its factorization.

1221010721161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157002912.

The product of its (nonzero) digits is 336, while the sum is 25.

Adding to 1221010721161 its reverse (1611270101221), we get a palindrome (2832280822382).

The spelling of 1221010721161 in words is "one trillion, two hundred twenty-one billion, ten million, seven hundred twenty-one thousand, one hundred sixty-one".