21724023 has 8 divisors (see below), whose sum is σ = 29264368. Its totient is φ = 14333184.

The previous prime is 21724019. The next prime is 21724037. The reversal of 21724023 is 32042712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21724023 - 2² = 21724019 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 (21714023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 37036 + ... + 37617.

It is an arithmetic number, because the mean of its divisors is an integer number (3658046).

Almost surely, 2^21724023 is an apocalyptic number.

21724023 is a deficient number, since it is larger than the sum of its proper divisors (7540345).

21724023 is an equidigital number, since it uses as much as digits as its factorization.

21724023 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74753.

The product of its (nonzero) digits is 672, while the sum is 21.

The square root of 21724023 is about 4660.9036677451. The cubic root of 21724023 is about 279.0273351000.

Adding to 21724023 its reverse (32042712), we get a palindrome (53766735).

The spelling of 21724023 in words is "twenty-one million, seven hundred twenty-four thousand, twenty-three".