21181005 has 12 divisors (see below), whose sum is σ = 36713820. Its totient is φ = 11296512.

The previous prime is 21181003. The next prime is 21181007. The reversal of 21181005 is 50018112.

It is an interprime number because it is at equal distance from previous prime (21181003) and next prime (21181007).

It can be written as a sum of positive squares in 2 ways, for example, as 7851204 + 13329801 = 2802^2 + 3651^2 .

It is not a de Polignac number, because 21181005 - 2¹ = 21181003 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21181001) 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 11 ways as a sum of consecutive naturals, for example, 235300 + ... + 235389.

It is an arithmetic number, because the mean of its divisors is an integer number (3059485).

Almost surely, 2^21181005 is an apocalyptic number.

It is an amenable number.

21181005 is a deficient number, since it is larger than the sum of its proper divisors (15532815).

21181005 is a wasteful number, since it uses less digits than its factorization.

21181005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 470700 (or 470697 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 18.

The square root of 21181005 is about 4602.2825858480. The cubic root of 21181005 is about 276.6828162699.

Adding to 21181005 its reverse (50018112), we get a palindrome (71199117).

The spelling of 21181005 in words is "twenty-one million, one hundred eighty-one thousand, five".