21010020111 has 16 divisors (see below), whose sum is σ = 31220005120. Its totient is φ = 13964357880.

The previous prime is 21010020091. The next prime is 21010020113. The reversal of 21010020111 is 11102001012.

It is a happy number.

It is not a de Polignac number, because 21010020111 - 2⁶ = 21010020047 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21010020093 and 21010020102.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010020113) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1166515 + ... + 1184388.

It is an arithmetic number, because the mean of its divisors is an integer number (1951250320).

Almost surely, 2^21010020111 is an apocalyptic number.

21010020111 is a deficient number, since it is larger than the sum of its proper divisors (10209985009).

21010020111 is a wasteful number, since it uses less digits than its factorization.

21010020111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2351243 (or 2351237 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

Adding to 21010020111 its reverse (11102001012), we get a palindrome (32112021123).

The spelling of 21010020111 in words is "twenty-one billion, ten million, twenty thousand, one hundred eleven".