21724573 has 4 divisors (see below), whose sum is σ = 23395708. Its totient is φ = 20053440.

The previous prime is 21724553. The next prime is 21724607. The reversal of 21724573 is 37542712.

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 10252804 + 11471769 = 3202^2 + 3387^2 .

It is a cyclic number.

It is not a de Polignac number, because 21724573 - 2¹³ = 21716381 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 (21724553) 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, 835548 + ... + 835573.

It is an arithmetic number, because the mean of its divisors is an integer number (5848927).

Almost surely, 2^21724573 is an apocalyptic number.

It is an amenable number.

21724573 is a deficient number, since it is larger than the sum of its proper divisors (1671135).

21724573 is a wasteful number, since it uses less digits than its factorization.

21724573 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1671134.

The product of its digits is 11760, while the sum is 31.

The square root of 21724573 is about 4660.9626688057. The cubic root of 21724573 is about 279.0296898471.

The spelling of 21724573 in words is "twenty-one million, seven hundred twenty-four thousand, five hundred seventy-three".