21000332120021 has 4 divisors (see below), whose sum is σ = 21724481503500. Its totient is φ = 20276182736544.

The previous prime is 21000332119993. The next prime is 21000332120039. The reversal of 21000332120021 is 12002123300012.

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 6007646102500 + 14992686017521 = 2451050^2 + 3872039^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000332120021 - 2³⁸ = 20725454213077 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000332120051) 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, 362074691696 + ... + 362074691753.

It is an arithmetic number, because the mean of its divisors is an integer number (5431120375875).

Almost surely, 2^{21000332120021} is an apocalyptic number.

It is an amenable number.

21000332120021 is a deficient number, since it is larger than the sum of its proper divisors (724149383479).

21000332120021 is an equidigital number, since it uses as much as digits as its factorization.

21000332120021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724149383478.

The product of its (nonzero) digits is 144, while the sum is 17.

Adding to 21000332120021 its reverse (12002123300012), we get a palindrome (33002455420033).

The spelling of 21000332120021 in words is "twenty-one trillion, three hundred thirty-two million, one hundred twenty thousand, twenty-one".