21380005 has 4 divisors (see below), whose sum is σ = 25656012. Its totient is φ = 17104000.

The previous prime is 21379993. The next prime is 21380011. The reversal of 21380005 is 50008312.

It is a happy number.

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 5769604 + 15610401 = 2402^2 + 3951^2 .

It is not a de Polignac number, because 21380005 - 2⁵ = 21379973 is a prime.

It is a super-2 number, since 2×21380005² = 914209227600050, which contains 22 as substring.

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 3 ways as a sum of consecutive naturals, for example, 2137996 + ... + 2138005.

It is an arithmetic number, because the mean of its divisors is an integer number (6414003).

Almost surely, 2^21380005 is an apocalyptic number.

It is an amenable number.

21380005 is a deficient number, since it is larger than the sum of its proper divisors (4276007).

21380005 is an equidigital number, since it uses as much as digits as its factorization.

21380005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4276006.

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21380005 is about 4623.8517493536. The cubic root of 21380005 is about 277.5466144672.

Adding to 21380005 its reverse (50008312), we get a palindrome (71388317).

The spelling of 21380005 in words is "twenty-one million, three hundred eighty thousand, five".