21000021020021 has 4 divisors (see below), whose sum is σ = 21000128837472. Its totient is φ = 20999913202572.

The previous prime is 21000021019987. The next prime is 21000021020029. The reversal of 21000021020021 is 12002012000012.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21000021020021 - 2³⁴ = 20982841150837 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21000021019984 and 21000021020011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000021020029) 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 3 ways as a sum of consecutive naturals, for example, 53616035 + ... + 54006288.

It is an arithmetic number, because the mean of its divisors is an integer number (5250032209368).

Almost surely, 2^{21000021020021} is an apocalyptic number.

It is an amenable number.

21000021020021 is a deficient number, since it is larger than the sum of its proper divisors (107817451).

21000021020021 is a wasteful number, since it uses less digits than its factorization.

21000021020021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107817450.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21000021020021 its reverse (12002012000012), we get a palindrome (33002033020033).

The spelling of 21000021020021 in words is "twenty-one trillion, twenty-one million, twenty thousand, twenty-one".