21240505 has 32 divisors (see below), whose sum is σ = 30498048. Its totient is φ = 13996800.

The previous prime is 21240433. The next prime is 21240511. The reversal of 21240505 is 50504212.

It is not a de Polignac number, because 21240505 - 2⁷ = 21240377 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 43372 + ... + 43858.

It is an arithmetic number, because the mean of its divisors is an integer number (953064).

Almost surely, 2^21240505 is an apocalyptic number.

It is an amenable number.

21240505 is a deficient number, since it is larger than the sum of its proper divisors (9257543).

21240505 is a wasteful number, since it uses less digits than its factorization.

21240505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 577.

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 21240505 is about 4608.7422362289. The cubic root of 21240505 is about 276.9416525309.

Adding to 21240505 its reverse (50504212), we get a palindrome (71744717).

The spelling of 21240505 in words is "twenty-one million, two hundred forty thousand, five hundred five".