21002101020 has 144 divisors (see below), whose sum is σ = 66738672000. Its totient is φ = 5338884096.

The previous prime is 21002100997. The next prime is 21002101033. The reversal of 21002101020 is 2010120012.

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

It is a junction number, because it is equal to n+sod(n) for n = 21002100993 and 21002101011.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 386916 + ... + 437844.

It is an arithmetic number, because the mean of its divisors is an integer number (463463000).

Almost surely, 2^21002101020 is an apocalyptic number.

21002101020 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 21002101020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33369336000).

21002101020 is an abundant number, since it is smaller than the sum of its proper divisors (45736570980).

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

21002101020 is a wasteful number, since it uses less digits than its factorization.

21002101020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51052 (or 51047 counting only the distinct ones).

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

Adding to 21002101020 its reverse (2010120012), we get a palindrome (23012221032).

The spelling of 21002101020 in words is "twenty-one billion, two million, one hundred one thousand, twenty".