21249479 has 4 divisors (see below), whose sum is σ = 21384984. Its totient is φ = 21113976.

The previous prime is 21249443. The next prime is 21249523. The reversal of 21249479 is 97494212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21249479 - 2¹² = 21245383 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21242479) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 67517 + ... + 67830.

It is an arithmetic number, because the mean of its divisors is an integer number (5346246).

Almost surely, 2^21249479 is an apocalyptic number.

21249479 is a deficient number, since it is larger than the sum of its proper divisors (135505).

21249479 is a wasteful number, since it uses less digits than its factorization.

21249479 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135504.

The product of its digits is 36288, while the sum is 38.

The square root of 21249479 is about 4609.7157179158. The cubic root of 21249479 is about 276.9806491628.

The spelling of 21249479 in words is "twenty-one million, two hundred forty-nine thousand, four hundred seventy-nine".