21000209101 has 4 divisors (see below), whose sum is σ = 21004255132. Its totient is φ = 20996163072.

The previous prime is 21000209093. The next prime is 21000209117. The reversal of 21000209101 is 10190200012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6630193476 + 14370015625 = 81426^2 + 119875^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000209101 - 2³ = 21000209093 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000209141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2015220 + ... + 2025613.

It is an arithmetic number, because the mean of its divisors is an integer number (5251063783).

Almost surely, 2^21000209101 is an apocalyptic number.

It is an amenable number.

21000209101 is a deficient number, since it is larger than the sum of its proper divisors (4046031).

21000209101 is an equidigital number, since it uses as much as digits as its factorization.

21000209101 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4046030.

The product of its (nonzero) digits is 36, while the sum is 16.

Adding to 21000209101 its reverse (10190200012), we get a palindrome (31190409113).

The spelling of 21000209101 in words is "twenty-one billion, two hundred nine thousand, one hundred one".