21191249 has 4 divisors (see below), whose sum is σ = 21248436. Its totient is φ = 21134064.

The previous prime is 21191239. The next prime is 21191263. The reversal of 21191249 is 94219112.

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 17581249 + 3610000 = 4193^2 + 1900^2 .

It is a cyclic number.

It is not a de Polignac number, because 21191249 - 2²⁰ = 20142673 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21191239) 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 3 ways as a sum of consecutive naturals, for example, 28034 + ... + 28779.

It is an arithmetic number, because the mean of its divisors is an integer number (5312109).

Almost surely, 2^21191249 is an apocalyptic number.

It is an amenable number.

21191249 is a deficient number, since it is larger than the sum of its proper divisors (57187).

21191249 is an equidigital number, since it uses as much as digits as its factorization.

21191249 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57186.

The product of its digits is 1296, while the sum is 29.

The square root of 21191249 is about 4603.3953773275. The cubic root of 21191249 is about 276.7274141216.

The spelling of 21191249 in words is "twenty-one million, one hundred ninety-one thousand, two hundred forty-nine".