21111002021 has 4 divisors (see below), whose sum is σ = 21112813344. Its totient is φ = 21109190700.

The previous prime is 21111001993. The next prime is 21111002039. The reversal of 21111002021 is 12020011112.

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 21111002021 - 2¹⁰ = 21111000997 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21111001993 and 21111002011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111022021) 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, 888065 + ... + 911526.

It is an arithmetic number, because the mean of its divisors is an integer number (5278203336).

Almost surely, 2^21111002021 is an apocalyptic number.

It is an amenable number.

21111002021 is a deficient number, since it is larger than the sum of its proper divisors (1811323).

21111002021 is a wasteful number, since it uses less digits than its factorization.

21111002021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1811322.

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

Adding to 21111002021 its reverse (12020011112), we get a palindrome (33131013133).

Subtracting from 21111002021 its reverse (12020011112), we obtain a palindrome (9090990909).

The spelling of 21111002021 in words is "twenty-one billion, one hundred eleven million, two thousand, twenty-one".