21010021111 has 4 divisors (see below), whose sum is σ = 21218041224. Its totient is φ = 20802001000.

The previous prime is 21010021091. The next prime is 21010021121. The reversal of 21010021111 is 11112001012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21010021111 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010021121) 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, 104009905 + ... + 104010106.

It is an arithmetic number, because the mean of its divisors is an integer number (5304510306).

Almost surely, 2^21010021111 is an apocalyptic number.

21010021111 is a deficient number, since it is larger than the sum of its proper divisors (208020113).

21010021111 is a wasteful number, since it uses less digits than its factorization.

21010021111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208020112.

The product of its (nonzero) digits is 4, while the sum is 10.

Adding to 21010021111 its reverse (11112001012), we get a palindrome (32122022123).

The spelling of 21010021111 in words is "twenty-one billion, ten million, twenty-one thousand, one hundred eleven".