21002120111 has 16 divisors (see below), whose sum is σ = 25456608768. Its totient is φ = 16936840800.

The previous prime is 21002120089. The next prime is 21002120129. The reversal of 21002120111 is 11102120012.

It is a cyclic number.

It is not a de Polignac number, because 21002120111 - 2¹⁸ = 21001857967 is a prime.

It is a super-4 number, since 4×21002120111⁴ (a number of 42 digits) contains 4444 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21002120092 and 21002120101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002120171) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1059425 + ... + 1079066.

It is an arithmetic number, because the mean of its divisors is an integer number (1591038048).

Almost surely, 2^21002120111 is an apocalyptic number.

21002120111 is a deficient number, since it is larger than the sum of its proper divisors (4454488657).

21002120111 is a wasteful number, since it uses less digits than its factorization.

21002120111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2138582.

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

Adding to 21002120111 its reverse (11102120012), we get a palindrome (32104240123).

Subtracting from 21002120111 its reverse (11102120012), we obtain a palindrome (9900000099).

The spelling of 21002120111 in words is "twenty-one billion, two million, one hundred twenty thousand, one hundred eleven".