21000212009 has 4 divisors (see below), whose sum is σ = 24000242304. Its totient is φ = 18000181716.

The previous prime is 21000211993. The next prime is 21000212027. The reversal of 21000212009 is 90021200012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21000212009 - 2⁴ = 21000211993 is a prime.

It is a super-3 number, since 3×21000212009³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21000212309) 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, 1500015137 + ... + 1500015150.

It is an arithmetic number, because the mean of its divisors is an integer number (6000060576).

Almost surely, 2^21000212009 is an apocalyptic number.

It is an amenable number.

21000212009 is a deficient number, since it is larger than the sum of its proper divisors (3000030295).

21000212009 is an equidigital number, since it uses as much as digits as its factorization.

21000212009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3000030294.

The product of its (nonzero) digits is 72, while the sum is 17.

The spelling of 21000212009 in words is "twenty-one billion, two hundred twelve thousand, nine".