21000000020121 has 8 divisors (see below), whose sum is σ = 31111111140960. Its totient is φ = 14000000013396.

The previous prime is 21000000020119. The next prime is 21000000020143. The reversal of 21000000020121 is 12102000000012.

It is not a de Polignac number, because 21000000020121 - 2¹ = 21000000020119 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (21000000020101) 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, 388888889235 + ... + 388888889288.

It is an arithmetic number, because the mean of its divisors is an integer number (3888888892620).

Almost surely, 2^{21000000020121} is an apocalyptic number.

It is an amenable number.

21000000020121 is a deficient number, since it is larger than the sum of its proper divisors (10111111120839).

21000000020121 is an equidigital number, since it uses as much as digits as its factorization.

21000000020121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 777777778532 (or 777777778526 counting only the distinct ones).

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

Adding to 21000000020121 its reverse (12102000000012), we get a palindrome (33102000020133).

The spelling of 21000000020121 in words is "twenty-one trillion, twenty thousand, one hundred twenty-one".