21139249 has 4 divisors (see below), whose sum is σ = 21326436. Its totient is φ = 20952064.

The previous prime is 21139243. The next prime is 21139253. The reversal of 21139249 is 94293112.

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 2347024 + 18792225 = 1532^2 + 4335^2 .

It is a cyclic number.

It is not a de Polignac number, because 21139249 - 2⁹ = 21138737 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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 21139249.

It is not an unprimeable number, because it can be changed into a prime (21139243) 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, 93424 + ... + 93649.

It is an arithmetic number, because the mean of its divisors is an integer number (5331609).

Almost surely, 2^21139249 is an apocalyptic number.

It is an amenable number.

21139249 is a deficient number, since it is larger than the sum of its proper divisors (187187).

21139249 is a wasteful number, since it uses less digits than its factorization.

21139249 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 187186.

The product of its digits is 3888, while the sum is 31.

The square root of 21139249 is about 4597.7439032639. The cubic root of 21139249 is about 276.5008801762.

The spelling of 21139249 in words is "twenty-one million, one hundred thirty-nine thousand, two hundred forty-nine".