21573723 has 4 divisors (see below), whose sum is σ = 28764968. Its totient is φ = 14382480.

The previous prime is 21573719. The next prime is 21573751. The reversal of 21573723 is 32737512.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21573723 - 2² = 21573719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21573023) 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, 3595618 + ... + 3595623.

It is an arithmetic number, because the mean of its divisors is an integer number (7191242).

Almost surely, 2^21573723 is an apocalyptic number.

21573723 is a deficient number, since it is larger than the sum of its proper divisors (7191245).

21573723 is an equidigital number, since it uses as much as digits as its factorization.

21573723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7191244.

The product of its digits is 8820, while the sum is 30.

The square root of 21573723 is about 4644.7522000641. The cubic root of 21573723 is about 278.3823517557.

The spelling of 21573723 in words is "twenty-one million, five hundred seventy-three thousand, seven hundred twenty-three".