21000000020021 has 8 divisors (see below), whose sum is σ = 22914469965600. Its totient is φ = 19086426580240.

The previous prime is 21000000019997. The next prime is 21000000020029. The reversal of 21000000020021 is 12002000000012.

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 21000000020021 - 2³⁴ = 20982820150837 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21000000019990 and 21000000020008.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000000020029) 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, 224077466 + ... + 224171163.

It is an arithmetic number, because the mean of its divisors is an integer number (2864308745700).

Almost surely, 2^{21000000020021} is an apocalyptic number.

It is an amenable number.

21000000020021 is a deficient number, since it is larger than the sum of its proper divisors (1914469945579).

21000000020021 is a wasteful number, since it uses less digits than its factorization.

21000000020021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 448252899.

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

Adding to 21000000020021 its reverse (12002000000012), we get a palindrome (33002000020033).

The spelling of 21000000020021 in words is "twenty-one trillion, twenty thousand, twenty-one".