21001000110021 has 12 divisors (see below), whose sum is σ = 30334817921772. Its totient is φ = 14000648285376.

The previous prime is 21001000110007. The next prime is 21001000110029. The reversal of 21001000110021 is 12001100010012.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 13926256604100 + 7074743505921 = 3731790^2 + 2659839^2 .

It is not a de Polignac number, because 21001000110021 - 2⁵ = 21001000109989 is a prime.

It is a super-2 number, since 2×21001000110021² (a number of 27 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21001000109985 and 21001000110012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001000110029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 11381895 + ... + 13097691.

It is an arithmetic number, because the mean of its divisors is an integer number (2527901493481).

Almost surely, 2^{21001000110021} is an apocalyptic number.

It is an amenable number.

21001000110021 is a deficient number, since it is larger than the sum of its proper divisors (9333817811751).

21001000110021 is a wasteful number, since it uses less digits than its factorization.

21001000110021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3075780 (or 3075777 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

Adding to 21001000110021 its reverse (12001100010012), we get a palindrome (33002100120033).

The spelling of 21001000110021 in words is "twenty-one trillion, one billion, one hundred ten thousand, twenty-one".