21129449 has 4 divisors (see below), whose sum is σ = 23050320. Its totient is φ = 19208580.

The previous prime is 21129439. The next prime is 21129467. The reversal of 21129449 is 94492112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21129449 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 (21129439) 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, 960419 + ... + 960440.

It is an arithmetic number, because the mean of its divisors is an integer number (5762580).

Almost surely, 2^21129449 is an apocalyptic number.

It is an amenable number.

21129449 is a deficient number, since it is larger than the sum of its proper divisors (1920871).

21129449 is a wasteful number, since it uses less digits than its factorization.

21129449 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1920870.

The product of its digits is 5184, while the sum is 32.

The square root of 21129449 is about 4596.6780396282. The cubic root of 21129449 is about 276.4581456485.

The spelling of 21129449 in words is "twenty-one million, one hundred twenty-nine thousand, four hundred forty-nine".