21009011 has 4 divisors (see below), whose sum is σ = 21019152. Its totient is φ = 20998872.

The previous prime is 21008941. The next prime is 21009017. The reversal of 21009011 is 11090012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21009011 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21009017) 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, 716 + ... + 6521.

It is an arithmetic number, because the mean of its divisors is an integer number (5254788).

Almost surely, 2^21009011 is an apocalyptic number.

21009011 is a deficient number, since it is larger than the sum of its proper divisors (10141).

21009011 is an equidigital number, since it uses as much as digits as its factorization.

21009011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10140.

The product of its (nonzero) digits is 18, while the sum is 14.

The square root of 21009011 is about 4583.5587702134. The cubic root of 21009011 is about 275.9318733694.

Adding to 21009011 its reverse (11090012), we get a palindrome (32099023).

It can be divided in two parts, 2100 and 9011, that added together give a palindrome (11111).

The spelling of 21009011 in words is "twenty-one million, nine thousand, eleven".