21215011 has 4 divisors (see below), whose sum is σ = 21224224. Its totient is φ = 21205800.

The previous prime is 21215009. The next prime is 21215017. The reversal of 21215011 is 11051212.

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 not a de Polignac number, because 21215011 - 2¹ = 21215009 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21214982 and 21215000.

It is not an unprimeable number, because it can be changed into a prime (21215017) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2281 + ... + 6901.

It is an arithmetic number, because the mean of its divisors is an integer number (5306056).

Almost surely, 2^21215011 is an apocalyptic number.

21215011 is a deficient number, since it is larger than the sum of its proper divisors (9213).

21215011 is an equidigital number, since it uses as much as digits as its factorization.

21215011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9212.

The product of its (nonzero) digits is 20, while the sum is 13.

The square root of 21215011 is about 4605.9755752718. The cubic root of 21215011 is about 276.8308080678.

Adding to 21215011 its reverse (11051212), we get a palindrome (32266223).

The spelling of 21215011 in words is "twenty-one million, two hundred fifteen thousand, eleven".