21002123311021 has 4 divisors (see below), whose sum is σ = 21002153961532. Its totient is φ = 21002092660512.

The previous prime is 21002123311019. The next prime is 21002123311079. The reversal of 21002123311021 is 12011332120012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2911681513225 + 18090441797796 = 1706365^2 + 4253286^2 .

It is a cyclic number.

It is not a de Polignac number, because 21002123311021 - 2¹ = 21002123311019 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21002123311021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002123411021) 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, 14273370 + ... + 15675883.

It is an arithmetic number, because the mean of its divisors is an integer number (5250538490383).

Almost surely, 2^{21002123311021} is an apocalyptic number.

It is an amenable number.

21002123311021 is a deficient number, since it is larger than the sum of its proper divisors (30650511).

21002123311021 is an equidigital number, since it uses as much as digits as its factorization.

21002123311021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30650510.

The product of its (nonzero) digits is 144, while the sum is 19.

Adding to 21002123311021 its reverse (12011332120012), we get a palindrome (33013455431033).

The spelling of 21002123311021 in words is "twenty-one trillion, two billion, one hundred twenty-three million, three hundred eleven thousand, twenty-one".