21111001001 has 4 divisors (see below), whose sum is σ = 21111435732. Its totient is φ = 21110566272.

The previous prime is 21111000997. The next prime is 21111001057. The reversal of 21111001001 is 10010011112.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 20841253225 + 269747776 = 144365^2 + 16424^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111001001 - 2² = 21111000997 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21111001001.

It is not an unprimeable number, because it can be changed into a prime (21111001601) 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, 133820 + ... + 245213.

It is an arithmetic number, because the mean of its divisors is an integer number (5277858933).

Almost surely, 2^21111001001 is an apocalyptic number.

It is an amenable number.

21111001001 is a deficient number, since it is larger than the sum of its proper divisors (434731).

21111001001 is an equidigital number, since it uses as much as digits as its factorization.

21111001001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 434730.

The product of its (nonzero) digits is 2, while the sum is 8.

Adding to 21111001001 its reverse (10010011112), we get a palindrome (31121012113).

The spelling of 21111001001 in words is "twenty-one billion, one hundred eleven million, one thousand, one".