21123011011 has 4 divisors (see below), whose sum is σ = 21130782400. Its totient is φ = 21115239624.

The previous prime is 21123010957. The next prime is 21123011033. The reversal of 21123011011 is 11011032112.

It is a happy number.

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 21123011011 - 2⁹ = 21123010499 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21123010982 and 21123011000.

It is not an unprimeable number, because it can be changed into a prime (21123011051) 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, 3881616 + ... + 3887053.

It is an arithmetic number, because the mean of its divisors is an integer number (5282695600).

Almost surely, 2^21123011011 is an apocalyptic number.

21123011011 is a deficient number, since it is larger than the sum of its proper divisors (7771389).

21123011011 is an equidigital number, since it uses as much as digits as its factorization.

21123011011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7771388.

The product of its (nonzero) digits is 12, while the sum is 13.

Adding to 21123011011 its reverse (11011032112), we get a palindrome (32134043123).

The spelling of 21123011011 in words is "twenty-one billion, one hundred twenty-three million, eleven thousand, eleven".