21000000210021 has 48 divisors (see below), whose sum is σ = 35322678443520. Its totient is φ = 11772943902720.

The previous prime is 21000000210011. The next prime is 21000000210037. The reversal of 21000000210021 is 12001200000012.

It is not a de Polignac number, because 21000000210021 - 2⁵ = 21000000209989 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

21000000210021 is a modest number, since divided by 210021 gives 210000 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 21000000209985 and 21000000210012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000000210011) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 64852165 + ... + 65175173.

It is an arithmetic number, because the mean of its divisors is an integer number (735889134240).

Almost surely, 2^{21000000210021} is an apocalyptic number.

21000000210021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21000000210021 is a deficient number, since it is larger than the sum of its proper divisors (14322678233499).

21000000210021 is a wasteful number, since it uses less digits than its factorization.

21000000210021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 342546 (or 342543 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21000000210021 its reverse (12001200000012), we get a palindrome (33001200210033).

The spelling of 21000000210021 in words is "twenty-one trillion, two hundred ten thousand, twenty-one".