21210111100081 has 2 divisors, whose sum is σ = 21210111100082. Its totient is φ = 21210111100080.

The previous prime is 21210111100043. The next prime is 21210111100133. The reversal of 21210111100081 is 18000111101212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16620983149456 + 4589127950625 = 4076884^2 + 2142225^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21210111100081 is a prime.

It is a super-2 number, since 2×21210111100081² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21210111100021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605055550040 + 10605055550041.

It is an arithmetic number, because the mean of its divisors is an integer number (10605055550041).

Almost surely, 2^{21210111100081} is an apocalyptic number.

It is an amenable number.

21210111100081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210111100081 is an equidigital number, since it uses as much as digits as its factorization.

21210111100081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 19.

Adding to 21210111100081 its reverse (18000111101212), we get a palindrome (39210222201293).

The spelling of 21210111100081 in words is "twenty-one trillion, two hundred ten billion, one hundred eleven million, one hundred thousand, eighty-one".