21020021111 has 4 divisors (see below), whose sum is σ = 21020946672. Its totient is φ = 21019095552.

The previous prime is 21020021101. The next prime is 21020021131. The reversal of 21020021111 is 11112002012.

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 21020021111 - 2¹⁸ = 21019758967 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21020021092 and 21020021101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020021101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 427835 + ... + 474428.

It is an arithmetic number, because the mean of its divisors is an integer number (5255236668).

Almost surely, 2^21020021111 is an apocalyptic number.

21020021111 is a deficient number, since it is larger than the sum of its proper divisors (925561).

21020021111 is an equidigital number, since it uses as much as digits as its factorization.

21020021111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 925560.

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

Adding to 21020021111 its reverse (11112002012), we get a palindrome (32132023123).

The spelling of 21020021111 in words is "twenty-one billion, twenty million, twenty-one thousand, one hundred eleven".