21111009 has 4 divisors (see below), whose sum is σ = 28148016. Its totient is φ = 14074004.

The previous prime is 21111007. The next prime is 21111029. The reversal of 21111009 is 90011112.

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 21111009 - 2¹ = 21111007 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21111007) 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, 3518499 + ... + 3518504.

It is an arithmetic number, because the mean of its divisors is an integer number (7037004).

Almost surely, 2^21111009 is an apocalyptic number.

It is an amenable number.

21111009 is a deficient number, since it is larger than the sum of its proper divisors (7037007).

21111009 is an equidigital number, since it uses as much as digits as its factorization.

21111009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7037006.

The product of its (nonzero) digits is 18, while the sum is 15.

The square root of 21111009 is about 4594.6718054721. The cubic root of 21111009 is about 276.3776991285.

The spelling of 21111009 in words is "twenty-one million, one hundred eleven thousand, nine".