21001123121 has 12 divisors (see below), whose sum is σ = 23088680832. Its totient is φ = 19087959000.

The previous prime is 21001123109. The next prime is 21001123177. The reversal of 21001123121 is 12132110012.

It is not a de Polignac number, because 21001123121 - 2²² = 20996928817 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001123096 and 21001123105.

It is not an unprimeable number, because it can be changed into a prime (21001125121) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 675836 + ... + 706226.

It is an arithmetic number, because the mean of its divisors is an integer number (1924056736).

Almost surely, 2^21001123121 is an apocalyptic number.

It is an amenable number.

21001123121 is a deficient number, since it is larger than the sum of its proper divisors (2087557711).

21001123121 is a wasteful number, since it uses less digits than its factorization.

21001123121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36124 (or 36113 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 14.

Adding to 21001123121 its reverse (12132110012), we get a palindrome (33133233133).

The spelling of 21001123121 in words is "twenty-one billion, one million, one hundred twenty-three thousand, one hundred twenty-one".