21201000021 has 10 divisors (see below), whose sum is σ = 31670629782. Its totient is φ = 14133999960.

The previous prime is 21201000017. The next prime is 21201000061. The reversal of 21201000021 is 12000010212.

It can be written as a sum of positive squares in only one way, i.e., 16948134225 + 4252865796 = 130185^2 + 65214^2 .

It is not a de Polignac number, because 21201000021 - 2² = 21201000017 is a prime.

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

It is a junction number, because it is equal to n+sod(n) for n = 21200999967 and 21201000012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201000011) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 130870290 + ... + 130870451.

Almost surely, 2^21201000021 is an apocalyptic number.

It is an amenable number.

21201000021 is a deficient number, since it is larger than the sum of its proper divisors (10469629761).

21201000021 is an equidigital number, since it uses as much as digits as its factorization.

21201000021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261740753 (or 261740744 counting only the distinct ones).

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

Adding to 21201000021 its reverse (12000010212), we get a palindrome (33201010233).

The spelling of 21201000021 in words is "twenty-one billion, two hundred one million, twenty-one", and thus it is an aban number.