21001000121 has 8 divisors (see below), whose sum is σ = 21455613504. Its totient is φ = 20550538800.

The previous prime is 21001000079. The next prime is 21001000129. The reversal of 21001000121 is 12100010012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21001000121 - 2²⁶ = 20933891257 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001000099 and 21001000108.

It is not an unprimeable number, because it can be changed into a prime (21001000129) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1027790 + ... + 1048023.

It is an arithmetic number, because the mean of its divisors is an integer number (2681951688).

Almost surely, 2^21001000121 is an apocalyptic number.

It is an amenable number.

21001000121 is a deficient number, since it is larger than the sum of its proper divisors (454613383).

21001000121 is a wasteful number, since it uses less digits than its factorization.

21001000121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2076031.

The product of its (nonzero) digits is 4, while the sum is 8.

Adding to 21001000121 its reverse (12100010012), we get a palindrome (33101010133).

The spelling of 21001000121 in words is "twenty-one billion, one million, one hundred twenty-one", and thus it is an aban number.