21212101 has 2 divisors, whose sum is σ = 21212102. Its totient is φ = 21212100.

The previous prime is 21212099. The next prime is 21212111. The reversal of 21212101 is 10121212.

21212101 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.

It is an a-pointer prime, because the next prime (21212111) can be obtained adding 21212101 to its sum of digits (10).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11383876 + 9828225 = 3374^2 + 3135^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212101 - 2¹ = 21212099 is a prime.

It is a super-3 number, since 3×21212101³ (a number of 23 digits) contains 333 as substring.

Together with 21212099, it forms a pair of twin primes.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21212111) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606050 + 10606051.

It is an arithmetic number, because the mean of its divisors is an integer number (10606051).

Almost surely, 2^21212101 is an apocalyptic number.

It is an amenable number.

21212101 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212101 is an equidigital number, since it uses as much as digits as its factorization.

21212101 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8, while the sum is 10.

The square root of 21212101 is about 4605.6596704490. The cubic root of 21212101 is about 276.8181501360.

Adding to 21212101 its reverse (10121212), we get a palindrome (31333313).

It can be divided in two parts, 21212 and 101, that multiplied together give a palindrome (2142412).

The spelling of 21212101 in words is "twenty-one million, two hundred twelve thousand, one hundred one".