21020120100 has 216 divisors, whose sum is σ = 75430380480. Its totient is φ = 4796202240.

The previous prime is 21020120087. The next prime is 21020120111. The reversal of 21020120100 is 102102012.

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

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 4048306 + ... + 4053494.

Almost surely, 2^21020120100 is an apocalyptic number.

21020120100 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 21020120100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37715190240).

21020120100 is an abundant number, since it is smaller than the sum of its proper divisors (54410260380).

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

21020120100 is a wasteful number, since it uses less digits than its factorization.

21020120100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5859 (or 5849 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21020120100 its reverse (102102012), we get a palindrome (21122222112).

The spelling of 21020120100 in words is "twenty-one billion, twenty million, one hundred twenty thousand, one hundred".