21181245 has 16 divisors (see below), whose sum is σ = 33963072. Its totient is φ = 11272320.

The previous prime is 21181189. The next prime is 21181267. The reversal of 21181245 is 54218112.

It is not a de Polignac number, because 21181245 - 2⁷ = 21181117 is a prime.

It is a Curzon 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 15 ways as a sum of consecutive naturals, for example, 7329 + ... + 9801.

It is an arithmetic number, because the mean of its divisors is an integer number (2122692).

Almost surely, 2^21181245 is an apocalyptic number.

It is an amenable number.

21181245 is a deficient number, since it is larger than the sum of its proper divisors (12781827).

21181245 is a wasteful number, since it uses less digits than its factorization.

21181245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3052.

The product of its digits is 640, while the sum is 24.

The square root of 21181245 is about 4602.3086597924. The cubic root of 21181245 is about 276.6838612884.

Adding to 21181245 its reverse (54218112), we get a palindrome (75399357).

The spelling of 21181245 in words is "twenty-one million, one hundred eighty-one thousand, two hundred forty-five".