21111100181 has 2 divisors, whose sum is σ = 21111100182. Its totient is φ = 21111100180.

The previous prime is 21111100139. The next prime is 21111100289. The reversal of 21111100181 is 18100111112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14010509956 + 7100590225 = 118366^2 + 84265^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111100181 - 2⁶ = 21111100117 is a prime.

It is a super-2 number, since 2×21111100181² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21111100981) 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 as a sum of consecutive naturals, namely, 10555550090 + 10555550091.

It is an arithmetic number, because the mean of its divisors is an integer number (10555550091).

Almost surely, 2^21111100181 is an apocalyptic number.

It is an amenable number.

21111100181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111100181 is an equidigital number, since it uses as much as digits as its factorization.

21111100181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16, while the sum is 17.

Adding to 21111100181 its reverse (18100111112), we get a palindrome (39211211293).

The spelling of 21111100181 in words is "twenty-one billion, one hundred eleven million, one hundred thousand, one hundred eighty-one".