21011111121 has 128 divisors (see below), whose sum is σ = 40246972416. Its totient is φ = 9382625280.

The previous prime is 21011111119. The next prime is 21011111129. The reversal of 21011111121 is 12111111012.

It is not a de Polignac number, because 21011111121 - 2¹ = 21011111119 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21011111097 and 21011111106.

It is not an unprimeable number, because it can be changed into a prime (21011111129) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 4949826 + ... + 4954068.

It is an arithmetic number, because the mean of its divisors is an integer number (314429472).

Almost surely, 2^21011111121 is an apocalyptic number.

21011111121 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21011111121 is a deficient number, since it is larger than the sum of its proper divisors (19235861295).

21011111121 is a wasteful number, since it uses less digits than its factorization.

21011111121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4391.

The product of its (nonzero) digits is 4, while the sum is 12.

Adding to 21011111121 its reverse (12111111012), we get a palindrome (33122222133).

The spelling of 21011111121 in words is "twenty-one billion, eleven million, one hundred eleven thousand, one hundred twenty-one".