100211981 has 2 divisors, whose sum is σ = 100211982. Its totient is φ = 100211980.

The previous prime is 100211971. The next prime is 100212043. The reversal of 100211981 is 189112001.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 100200100 + 11881 = 10010^2 + 109^2 .

It is a cyclic number.

It is not a de Polignac number, because 100211981 - 2²⁶ = 33103117 is a prime.

It is a super-2 number, since 2×100211981² = 20084882271888722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is equal to p_5773010 and since 100211981 and 5773010 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (100211921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 50105990 + 50105991.

It is an arithmetic number, because the mean of its divisors is an integer number (50105991).

Almost surely, 2^100211981 is an apocalyptic number.

It is an amenable number.

100211981 is a deficient number, since it is larger than the sum of its proper divisors (1).

100211981 is an equidigital number, since it uses as much as digits as its factorization.

100211981 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 100211981 is about 10010.5934389526. The cubic root of 100211981 is about 464.4866280989.

Adding to 100211981 its reverse (189112001), we get a palindrome (289323982).

The spelling of 100211981 in words is "one hundred million, two hundred eleven thousand, nine hundred eighty-one".