21102021011 has 4 divisors (see below), whose sum is σ = 21356262312. Its totient is φ = 20847779712.

The previous prime is 21102020987. The next prime is 21102021019. The reversal of 21102021011 is 11012020112.

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-21102021011 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21102020983 and 21102021001.

It is not an unprimeable number, because it can be changed into a prime (21102021019) 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, 127120526 + ... + 127120691.

It is an arithmetic number, because the mean of its divisors is an integer number (5339065578).

Almost surely, 2^21102021011 is an apocalyptic number.

21102021011 is a deficient number, since it is larger than the sum of its proper divisors (254241301).

21102021011 is an equidigital number, since it uses as much as digits as its factorization.

21102021011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 254241300.

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

Adding to 21102021011 its reverse (11012020112), we get a palindrome (32114041123).

The spelling of 21102021011 in words is "twenty-one billion, one hundred two million, twenty-one thousand, eleven".