21071005 has 4 divisors (see below), whose sum is σ = 25285212. Its totient is φ = 16856800.

The previous prime is 21071003. The next prime is 21071009. The reversal of 21071005 is 50017012.

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 4334724 + 16736281 = 2082^2 + 4091^2 .

It is not a de Polignac number, because 21071005 - 2¹ = 21071003 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21071005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21071003) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2107096 + ... + 2107105.

It is an arithmetic number, because the mean of its divisors is an integer number (6321303).

Almost surely, 2^21071005 is an apocalyptic number.

It is an amenable number.

21071005 is a deficient number, since it is larger than the sum of its proper divisors (4214207).

21071005 is an equidigital number, since it uses as much as digits as its factorization.

21071005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4214206.

The product of its (nonzero) digits is 70, while the sum is 16.

The square root of 21071005 is about 4590.3164378940. The cubic root of 21071005 is about 276.2030161082.

Adding to 21071005 its reverse (50017012), we get a palindrome (71088017).

The spelling of 21071005 in words is "twenty-one million, seventy-one thousand, five".