21011505 has 16 divisors (see below), whose sum is σ = 33675264. Its totient is φ = 11187200.

The previous prime is 21011503. The next prime is 21011509. The reversal of 21011505 is 50511012.

It is not a de Polignac number, because 21011505 - 2¹ = 21011503 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is not an unprimeable number, because it can be changed into a prime (21011503) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16657 + ... + 17873.

It is an arithmetic number, because the mean of its divisors is an integer number (2104704).

Almost surely, 2^21011505 is an apocalyptic number.

It is an amenable number.

21011505 is a deficient number, since it is larger than the sum of its proper divisors (12663759).

21011505 is a wasteful number, since it uses less digits than its factorization.

21011505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2376.

The product of its (nonzero) digits is 50, while the sum is 15.

The square root of 21011505 is about 4583.8308214855. The cubic root of 21011505 is about 275.9427916505.

Adding to 21011505 its reverse (50511012), we get a palindrome (71522517).

The spelling of 21011505 in words is "twenty-one million, eleven thousand, five hundred five".