21001121021 has 16 divisors (see below), whose sum is σ = 22260437760. Its totient is φ = 19757675520.

The previous prime is 21001121017. The next prime is 21001121087. The reversal of 21001121021 is 12012110012.

It is a cyclic number.

It is not a de Polignac number, because 21001121021 - 2² = 21001121017 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001120993 and 21001121011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001121321) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1674245 + ... + 1686741.

It is an arithmetic number, because the mean of its divisors is an integer number (1391277360).

Almost surely, 2^21001121021 is an apocalyptic number.

It is an amenable number.

21001121021 is a deficient number, since it is larger than the sum of its proper divisors (1259316739).

21001121021 is a wasteful number, since it uses less digits than its factorization.

21001121021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13124.

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21001121021 its reverse (12012110012), we get a palindrome (33013231033).

The spelling of 21001121021 in words is "twenty-one billion, one million, one hundred twenty-one thousand, twenty-one".