21011002121 has 4 divisors (see below), whose sum is σ = 21012234000. Its totient is φ = 21009770244.

The previous prime is 21011002087. The next prime is 21011002141. The reversal of 21011002121 is 12120011012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21011002121 - 2³⁰ = 19937260297 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21011002141) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 589991 + ... + 624588.

It is an arithmetic number, because the mean of its divisors is an integer number (5253058500).

Almost surely, 2^21011002121 is an apocalyptic number.

It is an amenable number.

21011002121 is a deficient number, since it is larger than the sum of its proper divisors (1231879).

21011002121 is a wasteful number, since it uses less digits than its factorization.

21011002121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1231878.

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

Adding to 21011002121 its reverse (12120011012), we get a palindrome (33131013133).

The spelling of 21011002121 in words is "twenty-one billion, eleven million, two thousand, one hundred twenty-one".