21121012111 has 4 divisors (see below), whose sum is σ = 21121804512. Its totient is φ = 21120219712.

The previous prime is 21121012103. The next prime is 21121012189. The reversal of 21121012111 is 11121012112.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21121012111 - 2³ = 21121012103 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21121012091 and 21121012100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121012511) 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, 354775 + ... + 410008.

It is an arithmetic number, because the mean of its divisors is an integer number (5280451128).

Almost surely, 2^21121012111 is an apocalyptic number.

21121012111 is a deficient number, since it is larger than the sum of its proper divisors (792401).

21121012111 is an equidigital number, since it uses as much as digits as its factorization.

21121012111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 792400.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21121012111 its reverse (11121012112), we get a palindrome (32242024223).

Subtracting from 21121012111 its reverse (11121012112), we obtain a palindrome (9999999999).

The spelling of 21121012111 in words is "twenty-one billion, one hundred twenty-one million, twelve thousand, one hundred eleven".