21002121111 has 4 divisors (see below), whose sum is σ = 28002828152. Its totient is φ = 14001414072.

The previous prime is 21002121073. The next prime is 21002121157. The reversal of 21002121111 is 11112120012.

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

It is not a de Polignac number, because 21002121111 - 2²⁵ = 20968566679 is a prime.

It is a super-2 number, since 2×21002121111² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002121311) 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, 3500353516 + ... + 3500353521.

It is an arithmetic number, because the mean of its divisors is an integer number (7000707038).

Almost surely, 2^21002121111 is an apocalyptic number.

21002121111 is a deficient number, since it is larger than the sum of its proper divisors (7000707041).

21002121111 is an equidigital number, since it uses as much as digits as its factorization.

21002121111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7000707040.

The product of its (nonzero) digits is 8, while the sum is 12.

Adding to 21002121111 its reverse (11112120012), we get a palindrome (32114241123).

It can be divided in two parts, 210021 and 21111, that added together give a palindrome (231132).

The spelling of 21002121111 in words is "twenty-one billion, two million, one hundred twenty-one thousand, one hundred eleven".