21240005 has 32 divisors (see below), whose sum is σ = 28200960. Its totient is φ = 15301440.

The previous prime is 21240001. The next prime is 21240049. The reversal of 21240005 is 50004212.

It is not a de Polignac number, because 21240005 - 2² = 21240001 is a prime.

It is a super-2 number, since 2×21240005² = 902275624800050, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21240001) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 299120 + ... + 299190.

It is an arithmetic number, because the mean of its divisors is an integer number (881280).

Almost surely, 2^21240005 is an apocalyptic number.

It is an amenable number.

21240005 is a deficient number, since it is larger than the sum of its proper divisors (6960955).

21240005 is a wasteful number, since it uses less digits than its factorization.

21240005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 209.

The product of its (nonzero) digits is 80, while the sum is 14.

The square root of 21240005 is about 4608.6879911749. The cubic root of 21240005 is about 276.9394794514.

Adding to 21240005 its reverse (50004212), we get a palindrome (71244217).

The spelling of 21240005 in words is "twenty-one million, two hundred forty thousand, five".