21379521 has 4 divisors (see below), whose sum is σ = 28506032. Its totient is φ = 14253012.

The previous prime is 21379517. The next prime is 21379531. The reversal of 21379521 is 12597312.

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 not a de Polignac number, because 21379521 - 2² = 21379517 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 (21379531) 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, 3563251 + ... + 3563256.

It is an arithmetic number, because the mean of its divisors is an integer number (7126508).

Almost surely, 2^21379521 is an apocalyptic number.

It is an amenable number.

21379521 is a deficient number, since it is larger than the sum of its proper divisors (7126511).

21379521 is an equidigital number, since it uses as much as digits as its factorization.

21379521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7126510.

The product of its digits is 3780, while the sum is 30.

The square root of 21379521 is about 4623.7994117392. The cubic root of 21379521 is about 277.5445200871.

The spelling of 21379521 in words is "twenty-one million, three hundred seventy-nine thousand, five hundred twenty-one".