21123012100 has 72 divisors (see below), whose sum is σ = 46478275200. Its totient is φ = 8331273600.

The previous prime is 21123012049. The next prime is 21123012109. The reversal of 21123012100 is 121032112.

It is not an unprimeable number, because it can be changed into a prime (21123012109) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8759895 + ... + 8762305.

It is an arithmetic number, because the mean of its divisors is an integer number (645531600).

Almost surely, 2^21123012100 is an apocalyptic number.

21123012100 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 21123012100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23239137600).

21123012100 is an abundant number, since it is smaller than the sum of its proper divisors (25355263100).

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

21123012100 is a wasteful number, since it uses less digits than its factorization.

21123012100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3613 (or 3606 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 13.

Adding to 21123012100 its reverse (121032112), we get a palindrome (21244044212).

The spelling of 21123012100 in words is "twenty-one billion, one hundred twenty-three million, twelve thousand, one hundred".