21001001020021 has 36 divisors (see below), whose sum is σ = 24436242671232. Its totient is φ = 18032330646000.

The previous prime is 21001001020007. The next prime is 21001001020049. The reversal of 21001001020021 is 12002010010012.

It is not a de Polignac number, because 21001001020021 - 2³¹ = 20998853536373 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001001720021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 13732156 + ... + 15184666.

Almost surely, 2^{21001001020021} is an apocalyptic number.

It is an amenable number.

21001001020021 is a deficient number, since it is larger than the sum of its proper divisors (3435241651211).

21001001020021 is a wasteful number, since it uses less digits than its factorization.

21001001020021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1452902 (or 1452872 counting only the distinct ones).

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

Adding to 21001001020021 its reverse (12002010010012), we get a palindrome (33003011030033).

The spelling of 21001001020021 in words is "twenty-one trillion, one billion, one million, twenty thousand, twenty-one".