21121012021 has 2 divisors, whose sum is σ = 21121012022. Its totient is φ = 21121012020.

The previous prime is 21121011959. The next prime is 21121012037. The reversal of 21121012021 is 12021012112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17770223025 + 3350788996 = 133305^2 + 57886^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121012021 - 2³¹ = 18973528373 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21121011992 and 21121012010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21121019021) 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, 10560506010 + 10560506011.

It is an arithmetic number, because the mean of its divisors is an integer number (10560506011).

Almost surely, 2^21121012021 is an apocalyptic number.

It is an amenable number.

21121012021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121012021 is an equidigital number, since it uses as much as digits as its factorization.

21121012021 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 13.

Adding to 21121012021 its reverse (12021012112), we get a palindrome (33142024133).

Subtracting from 21121012021 its reverse (12021012112), we obtain a palindrome (9099999909).

The spelling of 21121012021 in words is "twenty-one billion, one hundred twenty-one million, twelve thousand, twenty-one".