21080005 has 4 divisors (see below), whose sum is σ = 25296012. Its totient is φ = 16864000.

The previous prime is 21079999. The next prime is 21080021. The reversal of 21080005 is 50008012.

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 10640644 + 10439361 = 3262^2 + 3231^2 .

It is not a de Polignac number, because 21080005 - 2³ = 21079997 is a prime.

It is a super-2 number, since 2×21080005² = 888733221600050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2107996 + ... + 2108005.

It is an arithmetic number, because the mean of its divisors is an integer number (6324003).

Almost surely, 2^21080005 is an apocalyptic number.

It is an amenable number.

21080005 is a deficient number, since it is larger than the sum of its proper divisors (4216007).

21080005 is an equidigital number, since it uses as much as digits as its factorization.

21080005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4216006.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 21080005 is about 4591.2966578081. The cubic root of 21080005 is about 276.2423351204.

Adding to 21080005 its reverse (50008012), we get a palindrome (71088017).

The spelling of 21080005 in words is "twenty-one million, eighty thousand, five".