21339521 has 4 divisors (see below), whose sum is σ = 24388032. Its totient is φ = 18291012.

The previous prime is 21339511. The next prime is 21339529. The reversal of 21339521 is 12593312.

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-21339521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21339529) 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, 1524245 + ... + 1524258.

It is an arithmetic number, because the mean of its divisors is an integer number (6097008).

Almost surely, 2^21339521 is an apocalyptic number.

It is an amenable number.

21339521 is a deficient number, since it is larger than the sum of its proper divisors (3048511).

21339521 is an equidigital number, since it uses as much as digits as its factorization.

21339521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3048510.

The product of its digits is 1620, while the sum is 26.

The square root of 21339521 is about 4619.4719395186. The cubic root of 21339521 is about 277.3713214510.

The spelling of 21339521 in words is "twenty-one million, three hundred thirty-nine thousand, five hundred twenty-one".