21001210100020 has 12 divisors (see below), whose sum is σ = 44102541210084. Its totient is φ = 8400484040000.

The previous prime is 21001210099999. The next prime is 21001210100029. The reversal of 21001210100020 is 2000101210012.

It can be written as a sum of positive squares in 2 ways, for example, as 5165601657616 + 15835608442404 = 2272796^2 + 3979398^2 .

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001210100029) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 525030252481 + ... + 525030252520.

It is an arithmetic number, because the mean of its divisors is an integer number (3675211767507).

Almost surely, 2^{21001210100020} is an apocalyptic number.

21001210100020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001210100020 is an abundant number, since it is smaller than the sum of its proper divisors (23101331110064).

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

21001210100020 is a wasteful number, since it uses less digits than its factorization.

21001210100020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1050060505010 (or 1050060505008 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21001210100020 its reverse (2000101210012), we get a palindrome (23001311310032).

The spelling of 21001210100020 in words is "twenty-one trillion, one billion, two hundred ten million, one hundred thousand, twenty".