21912005 has 8 divisors (see below), whose sum is σ = 26385912. Its totient is φ = 17468608.

The previous prime is 21911987. The next prime is 21912013. The reversal of 21912005 is 50021912.

It can be written as a sum of positive squares in 4 ways, for example, as 4456321 + 17455684 = 2111^2 + 4178^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21912005 - 2¹² = 21907909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6014 + ... + 8943.

It is an arithmetic number, because the mean of its divisors is an integer number (3298239).

Almost surely, 2^21912005 is an apocalyptic number.

It is an amenable number.

21912005 is a deficient number, since it is larger than the sum of its proper divisors (4473907).

21912005 is a wasteful number, since it uses less digits than its factorization.

21912005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15255.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 21912005 is about 4681.0260627345. The cubic root of 21912005 is about 279.8298498556.

Adding to 21912005 its reverse (50021912), we get a palindrome (71933917).

The spelling of 21912005 in words is "twenty-one million, nine hundred twelve thousand, five".