100121981 has 2 divisors, whose sum is σ = 100121982. Its totient is φ = 100121980.

The previous prime is 100121977. The next prime is 100122023. The reversal of 100121981 is 189121001.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76405081 + 23716900 = 8741^2 + 4870^2 .

It is an emirp because it is prime and its reverse (189121001) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 100121981 - 2² = 100121977 is a prime.

It is a super-2 number, since 2×100121981² = 20048822158728722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (100121911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 50060990 + 50060991.

It is an arithmetic number, because the mean of its divisors is an integer number (50060991).

Almost surely, 2^100121981 is an apocalyptic number.

It is an amenable number.

100121981 is a deficient number, since it is larger than the sum of its proper divisors (1).

100121981 is an equidigital number, since it uses as much as digits as its factorization.

100121981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 23.

The square root of 100121981 is about 10006.0971912130. The cubic root of 100121981 is about 464.3475352248.

Adding to 100121981 its reverse (189121001), we get a palindrome (289242982).

The spelling of 100121981 in words is "one hundred million, one hundred twenty-one thousand, nine hundred eighty-one".