21738505 has 4 divisors (see below), whose sum is σ = 26086212. Its totient is φ = 17390800.

The previous prime is 21738503. The next prime is 21738539. The reversal of 21738505 is 50583712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15468489 + 6270016 = 3933^2 + 2504^2 .

It is not a de Polignac number, because 21738505 - 2¹ = 21738503 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21738503) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 2173846 + ... + 2173855.

It is an arithmetic number, because the mean of its divisors is an integer number (6521553).

Almost surely, 2^21738505 is an apocalyptic number.

It is an amenable number.

21738505 is a deficient number, since it is larger than the sum of its proper divisors (4347707).

21738505 is an equidigital number, since it uses as much as digits as its factorization.

21738505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4347706.

The product of its (nonzero) digits is 8400, while the sum is 31.

The square root of 21738505 is about 4662.4569703108. The cubic root of 21738505 is about 279.0893244819.

The spelling of 21738505 in words is "twenty-one million, seven hundred thirty-eight thousand, five hundred five".