21002123121 has 16 divisors (see below), whose sum is σ = 32453987328. Its totient is φ = 11832181200.

The previous prime is 21002123111. The next prime is 21002123143. The reversal of 21002123121 is 12132120012.

It is not a de Polignac number, because 21002123121 - 2⁷ = 21002122993 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21002123121.

It is not an unprimeable number, because it can be changed into a prime (21002123111) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7041475 + ... + 7044456.

It is an arithmetic number, because the mean of its divisors is an integer number (2028374208).

Almost surely, 2^21002123121 is an apocalyptic number.

21002123121 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21002123121 is a deficient number, since it is larger than the sum of its proper divisors (11451864207).

21002123121 is a wasteful number, since it uses less digits than its factorization.

21002123121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14086012.

The product of its (nonzero) digits is 48, while the sum is 15.

Adding to 21002123121 its reverse (12132120012), we get a palindrome (33134243133).

The spelling of 21002123121 in words is "twenty-one billion, two million, one hundred twenty-three thousand, one hundred twenty-one".