1221115981 has 2 divisors, whose sum is σ = 1221115982. Its totient is φ = 1221115980.

The previous prime is 1221115969. The next prime is 1221115999. The reversal of 1221115981 is 1895111221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1207910025 + 13205956 = 34755^2 + 3634^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221115981 - 2⁵ = 1221115949 is a prime.

It is a super-2 number, since 2×1221115981² = 2982248478107184722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221115901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610557990 + 610557991.

It is an arithmetic number, because the mean of its divisors is an integer number (610557991).

Almost surely, 2^1221115981 is an apocalyptic number.

It is an amenable number.

1221115981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221115981 is an equidigital number, since it uses as much as digits as its factorization.

1221115981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 31.

The square root of 1221115981 is about 34944.4699630714. The cubic root of 1221115981 is about 1068.8554392924.

The spelling of 1221115981 in words is "one billion, two hundred twenty-one million, one hundred fifteen thousand, nine hundred eighty-one".