21001002121 has 6 divisors (see below), whose sum is σ = 23083746266. Its totient is φ = 19091820000.

The previous prime is 21001002109. The next prime is 21001002137. The reversal of 21001002121 is 12120010012.

It can be written as a sum of positive squares in only one way, i.e., 19762736400 + 1238265721 = 140580^2 + 35189^2 .

It is not a de Polignac number, because 21001002121 - 2⁵ = 21001002089 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001002098 and 21001002107.

It is not an unprimeable number, because it can be changed into a prime (21001002101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 86780880 + ... + 86781121.

Almost surely, 2^21001002121 is an apocalyptic number.

It is an amenable number.

21001002121 is a deficient number, since it is larger than the sum of its proper divisors (2082744145).

21001002121 is a wasteful number, since it uses less digits than its factorization.

21001002121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173562023 (or 173562012 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21001002121 its reverse (12120010012), we get a palindrome (33121012133).

The spelling of 21001002121 in words is "twenty-one billion, one million, two thousand, one hundred twenty-one".