21579973 has 4 divisors (see below), whose sum is σ = 22324140. Its totient is φ = 20835808.

The previous prime is 21579959. The next prime is 21579977. The reversal of 21579973 is 37997512.

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 7193124 + 14386849 = 2682^2 + 3793^2 .

It is a cyclic number.

It is not a de Polignac number, because 21579973 - 2⁹ = 21579461 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 (21579977) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 372040 + ... + 372097.

It is an arithmetic number, because the mean of its divisors is an integer number (5581035).

Almost surely, 2^21579973 is an apocalyptic number.

It is an amenable number.

21579973 is a deficient number, since it is larger than the sum of its proper divisors (744167).

21579973 is an equidigital number, since it uses as much as digits as its factorization.

21579973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 744166.

The product of its digits is 119070, while the sum is 43.

The square root of 21579973 is about 4645.4249536506. The cubic root of 21579973 is about 278.4092320135.

The spelling of 21579973 in words is "twenty-one million, five hundred seventy-nine thousand, nine hundred seventy-three".