21001020100 has 18 divisors (see below), whose sum is σ = 45572213834. Its totient is φ = 8400408000.

The previous prime is 21001020083. The next prime is 21001020107. The reversal of 21001020100 is 102010012.

It can be written as a sum of positive squares in 3 ways, for example, as 6635079936 + 14365940164 = 81456^2 + 119858^2 .

It is not an unprimeable number, because it can be changed into a prime (21001020107) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 105005001 + ... + 105005200.

Almost surely, 2^21001020100 is an apocalyptic number.

21001020100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001020100 is an abundant number, since it is smaller than the sum of its proper divisors (24571193734).

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

21001020100 is a wasteful number, since it uses less digits than its factorization.

21001020100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210010215 (or 210010208 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 7.

Adding to 21001020100 its reverse (102010012), we get a palindrome (21103030112).

The spelling of 21001020100 in words is "twenty-one billion, one million, twenty thousand, one hundred".