21011011123 has 4 divisors (see below), whose sum is σ = 21011762800. Its totient is φ = 21010259448.

The previous prime is 21011011111. The next prime is 21011011139. The reversal of 21011011123 is 32111011012.

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 21011011123 - 2²¹ = 21008913971 is a prime.

It is a super-2 number, since 2×21011011123² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21011011223) 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, 332223 + ... + 390376.

It is an arithmetic number, because the mean of its divisors is an integer number (5252940700).

Almost surely, 2^21011011123 is an apocalyptic number.

21011011123 is a deficient number, since it is larger than the sum of its proper divisors (751677).

21011011123 is an equidigital number, since it uses as much as digits as its factorization.

21011011123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 751676.

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

Adding to 21011011123 its reverse (32111011012), we get a palindrome (53122022135).

The spelling of 21011011123 in words is "twenty-one billion, eleven million, eleven thousand, one hundred twenty-three".