21168505 has 16 divisors (see below), whose sum is σ = 26869248. Its totient is φ = 15984000.

The previous prime is 21168491. The next prime is 21168509. The reversal of 21168505 is 50586112.

It is not a de Polignac number, because 21168505 - 2¹³ = 21160313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21168509) 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, 4690 + ... + 8020.

It is an arithmetic number, because the mean of its divisors is an integer number (1679328).

Almost surely, 2^21168505 is an apocalyptic number.

It is an amenable number.

21168505 is a deficient number, since it is larger than the sum of its proper divisors (5700743).

21168505 is a wasteful number, since it uses less digits than its factorization.

21168505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3408.

The product of its (nonzero) digits is 2400, while the sum is 28.

The square root of 21168505 is about 4600.9243636469. The cubic root of 21168505 is about 276.6283773079.

The spelling of 21168505 in words is "twenty-one million, one hundred sixty-eight thousand, five hundred five".