21111211100100 has 144 divisors (see below), whose sum is σ = 66671966221056. Its totient is φ = 5115003984000.

The previous prime is 21111211100099. The next prime is 21111211100101. The reversal of 21111211100100 is 100111211112.

It is an interprime number because it is at equal distance from previous prime (21111211100099) and next prime (21111211100101).

It is a super-2 number, since 2×21111211100100² (a number of 27 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is not an unprimeable number, because it can be changed into a prime (21111211100101) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 4107135 + ... + 7687065.

It is an arithmetic number, because the mean of its divisors is an integer number (462999765424).

Almost surely, 2^{21111211100100} is an apocalyptic number.

21111211100100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21111211100100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33335983110528).

21111211100100 is an abundant number, since it is smaller than the sum of its proper divisors (45560755120956).

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

21111211100100 is a wasteful number, since it uses less digits than its factorization.

21111211100100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3581746 (or 3581739 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 12.

Adding to 21111211100100 its reverse (100111211112), we get a palindrome (21211322311212).

The spelling of 21111211100100 in words is "twenty-one trillion, one hundred eleven billion, two hundred eleven million, one hundred thousand, one hundred".