21213240121 has 2 divisors, whose sum is σ = 21213240122. Its totient is φ = 21213240120.

The previous prime is 21213240107. The next prime is 21213240143. The reversal of 21213240121 is 12104231212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17751565225 + 3461674896 = 133235^2 + 58836^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213240121 - 2¹¹ = 21213238073 is a prime.

It is a super-3 number, since 3×21213240121³ (a number of 32 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21213240721) 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, 10606620060 + 10606620061.

It is an arithmetic number, because the mean of its divisors is an integer number (10606620061).

Almost surely, 2^21213240121 is an apocalyptic number.

It is an amenable number.

21213240121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21213240121 is an equidigital number, since it uses as much as digits as its factorization.

21213240121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 192, while the sum is 19.

Adding to 21213240121 its reverse (12104231212), we get a palindrome (33317471333).

The spelling of 21213240121 in words is "twenty-one billion, two hundred thirteen million, two hundred forty thousand, one hundred twenty-one".