21001112121020 has 72 divisors (see below), whose sum is σ = 46568273298624. Its totient is φ = 7954452888192.

The previous prime is 21001112120951. The next prime is 21001112121023. The reversal of 21001112121020 is 2012121110012.

It is a junction number, because it is equal to n+sod(n) for n = 21001112120986 and 21001112121004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001112121023) 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, 14189882 + ... + 15599838.

It is an arithmetic number, because the mean of its divisors is an integer number (646781573592).

Almost surely, 2^{21001112121020} is an apocalyptic number.

21001112121020 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 21001112121020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23284136649312).

21001112121020 is an abundant number, since it is smaller than the sum of its proper divisors (25567161177604).

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

21001112121020 is a wasteful number, since it uses less digits than its factorization.

21001112121020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1412067 (or 1412046 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 14.

Adding to 21001112121020 its reverse (2012121110012), we get a palindrome (23013233231032).

The spelling of 21001112121020 in words is "twenty-one trillion, one billion, one hundred twelve million, one hundred twenty-one thousand, twenty".