21045505 has 32 divisors (see below), whose sum is σ = 28576800. Its totient is φ = 14776320.

The previous prime is 21045487. The next prime is 21045517. The reversal of 21045505 is 50554012.

It can be written as a sum of positive squares in 16 ways, for example, as 15737089 + 5308416 = 3967^2 + 2304^2 .

It is not a de Polignac number, because 21045505 - 2⁷ = 21045377 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 141171 + ... + 141319.

It is an arithmetic number, because the mean of its divisors is an integer number (893025).

Almost surely, 2^21045505 is an apocalyptic number.

It is an amenable number.

21045505 is a deficient number, since it is larger than the sum of its proper divisors (7531295).

21045505 is a wasteful number, since it uses less digits than its factorization.

21045505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 261.

The product of its (nonzero) digits is 1000, while the sum is 22.

The square root of 21045505 is about 4587.5380107417. The cubic root of 21045505 is about 276.0915514038.

Adding to 21045505 its reverse (50554012), we get a palindrome (71599517).

The spelling of 21045505 in words is "twenty-one million, forty-five thousand, five hundred five".