21001021102021 has 8 divisors (see below), whose sum is σ = 21729730865400. Its totient is φ = 20272613780160.

The previous prime is 21001021101967. The next prime is 21001021102037. The reversal of 21001021102021 is 12020112010012.

It can be written as a sum of positive squares in 4 ways, for example, as 559183901796 + 20441837200225 = 747786^2 + 4521265^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21001021102021 - 2⁹ = 21001021101509 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001021101992 and 21001021102010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001021102051) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 75469090 + ... + 75746851.

It is an arithmetic number, because the mean of its divisors is an integer number (2716216358175).

Almost surely, 2^{21001021102021} is an apocalyptic number.

It is an amenable number.

21001021102021 is a deficient number, since it is larger than the sum of its proper divisors (728709763379).

21001021102021 is a wasteful number, since it uses less digits than its factorization.

21001021102021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151220759.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21001021102021 its reverse (12020112010012), we get a palindrome (33021133112033).

The spelling of 21001021102021 in words is "twenty-one trillion, one billion, twenty-one million, one hundred two thousand, twenty-one".