21121234021 has 4 divisors (see below), whose sum is σ = 21255764332. Its totient is φ = 20986703712.

The previous prime is 21121233989. The next prime is 21121234063. The reversal of 21121234021 is 12043212112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2409729921 + 18711504100 = 49089^2 + 136790^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121234021 - 2⁵ = 21121233989 is a prime.

It is a super-2 number, since 2×21121234021² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21121234021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121234621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 67264920 + ... + 67265233.

It is an arithmetic number, because the mean of its divisors is an integer number (5313941083).

Almost surely, 2^21121234021 is an apocalyptic number.

It is an amenable number.

21121234021 is a deficient number, since it is larger than the sum of its proper divisors (134530311).

21121234021 is a wasteful number, since it uses less digits than its factorization.

21121234021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134530310.

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

Adding to 21121234021 its reverse (12043212112), we get a palindrome (33164446133).

The spelling of 21121234021 in words is "twenty-one billion, one hundred twenty-one million, two hundred thirty-four thousand, twenty-one".