21111110161 has 2 divisors, whose sum is σ = 21111110162. Its totient is φ = 21111110160.

The previous prime is 21111110123. The next prime is 21111110231. The reversal of 21111110161 is 16101111112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19166741136 + 1944369025 = 138444^2 + 44095^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21111110161 is a prime.

It is a super-3 number, since 3×21111110161³ (a number of 32 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21111110261) 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, 10555555080 + 10555555081.

It is an arithmetic number, because the mean of its divisors is an integer number (10555555081).

Almost surely, 2^21111110161 is an apocalyptic number.

It is an amenable number.

21111110161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21111110161 is an equidigital number, since it uses as much as digits as its factorization.

21111110161 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12, while the sum is 16.

Adding to 21111110161 its reverse (16101111112), we get a palindrome (37212221273).

The spelling of 21111110161 in words is "twenty-one billion, one hundred eleven million, one hundred ten thousand, one hundred sixty-one".