21211021009 has 4 divisors (see below), whose sum is σ = 21421031220. Its totient is φ = 21001010800.

The previous prime is 21211021003. The next prime is 21211021081. The reversal of 21211021009 is 90012011212.

It is a happy number.

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 15267073600 + 5943947409 = 123560^2 + 77097^2 .

It is not a de Polignac number, because 21211021009 - 2⁵ = 21211020977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21211021003) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105004954 + ... + 105005155.

It is an arithmetic number, because the mean of its divisors is an integer number (5355257805).

Almost surely, 2^21211021009 is an apocalyptic number.

It is an amenable number.

21211021009 is a deficient number, since it is larger than the sum of its proper divisors (210010211).

21211021009 is a wasteful number, since it uses less digits than its factorization.

21211021009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210010210.

The product of its (nonzero) digits is 72, while the sum is 19.

The spelling of 21211021009 in words is "twenty-one billion, two hundred eleven million, twenty-one thousand, nine".