21104251 has 6 divisors (see below), whose sum is σ = 24549900. Its totient is φ = 18089316.

The previous prime is 21104249. The next prime is 21104267. The reversal of 21104251 is 15240112.

It is not a de Polignac number, because 21104251 - 2¹ = 21104249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21104221) 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 5 ways as a sum of consecutive naturals, for example, 215301 + ... + 215398.

It is an arithmetic number, because the mean of its divisors is an integer number (4091650).

Almost surely, 2^21104251 is an apocalyptic number.

21104251 is a deficient number, since it is larger than the sum of its proper divisors (3445649).

21104251 is an equidigital number, since it uses as much as digits as its factorization.

21104251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 430713 (or 430706 counting only the distinct ones).

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

The square root of 21104251 is about 4593.9363295544. The cubic root of 21104251 is about 276.3482048833.

Adding to 21104251 its reverse (15240112), we get a palindrome (36344363).

The spelling of 21104251 in words is "twenty-one million, one hundred four thousand, two hundred fifty-one".