21000121000021 has 4 divisors (see below), whose sum is σ = 21724263103500. Its totient is φ = 20275978896544.

The previous prime is 21000120999973. The next prime is 21000121000031. The reversal of 21000121000021 is 12000012100012.

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 14565710415025 + 6434410584996 = 3816505^2 + 2536614^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000121000021 - 2⁴¹ = 18801097744469 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21000120999971 and 21000121000007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000121000031) 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, 362071051696 + ... + 362071051753.

It is an arithmetic number, because the mean of its divisors is an integer number (5431065775875).

Almost surely, 2^{21000121000021} is an apocalyptic number.

It is an amenable number.

21000121000021 is a deficient number, since it is larger than the sum of its proper divisors (724142103479).

21000121000021 is an equidigital number, since it uses as much as digits as its factorization.

21000121000021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724142103478.

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

Adding to 21000121000021 its reverse (12000012100012), we get a palindrome (33000133100033).

The spelling of 21000121000021 in words is "twenty-one trillion, one hundred twenty-one million, twenty-one", and thus it is an aban number.