21750005 has 8 divisors (see below), whose sum is σ = 26216352. Its totient is φ = 17322448.

The previous prime is 21749999. The next prime is 21750007. The reversal of 21750005 is 50005712.

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 21750005 - 2⁴ = 21749989 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21750007) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8447 + ... + 10716.

It is an arithmetic number, because the mean of its divisors is an integer number (3277044).

Almost surely, 2^21750005 is an apocalyptic number.

It is an amenable number.

21750005 is a deficient number, since it is larger than the sum of its proper divisors (4466347).

21750005 is a wasteful number, since it uses less digits than its factorization.

21750005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19395.

The product of its (nonzero) digits is 350, while the sum is 20.

The square root of 21750005 is about 4663.6900626006. The cubic root of 21750005 is about 279.1385299728.

Adding to 21750005 its reverse (50005712), we get a palindrome (71755717).

The spelling of 21750005 in words is "twenty-one million, seven hundred fifty thousand, five".