21001120021 has 16 divisors (see below), whose sum is σ = 24114384000. Its totient is φ = 17916326208.

The previous prime is 21001120013. The next prime is 21001120073. The reversal of 21001120021 is 12002110012.

It is a cyclic number.

It is not a de Polignac number, because 21001120021 - 2³ = 21001120013 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001120421) 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 in 15 ways as a sum of consecutive naturals, for example, 1367775 + ... + 1383043.

It is an arithmetic number, because the mean of its divisors is an integer number (1507149000).

Almost surely, 2^21001120021 is an apocalyptic number.

It is an amenable number.

21001120021 is a deficient number, since it is larger than the sum of its proper divisors (3113263979).

21001120021 is a wasteful number, since it uses less digits than its factorization.

21001120021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16188.

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

Adding to 21001120021 its reverse (12002110012), we get a palindrome (33003230033).

It can be divided in two parts, 210011 and 20021, that added together give a palindrome (230032).

The spelling of 21001120021 in words is "twenty-one billion, one million, one hundred twenty thousand, twenty-one".