21111002100 has 54 divisors (see below), whose sum is σ = 66171266070. Its totient is φ = 5629600320.

The previous prime is 21111002063. The next prime is 21111002117. The reversal of 21111002100 is 120011112.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 38415204 + 21072586896 = 6198^2 + 145164^2 .

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

It is a congruent number.

It is an unprimeable number.

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 17 ways as a sum of consecutive naturals, for example, 11727435 + ... + 11729234.

Almost surely, 2^21111002100 is an apocalyptic number.

21111002100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21111002100 is an abundant number, since it is smaller than the sum of its proper divisors (45060263970).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21111002100 is a wasteful number, since it uses less digits than its factorization.

21111002100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23456689 (or 23456679 counting only the distinct ones).

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

Adding to 21111002100 its reverse (120011112), we get a palindrome (21231013212).

The spelling of 21111002100 in words is "twenty-one billion, one hundred eleven million, two thousand, one hundred".