21724741 has 4 divisors (see below), whose sum is σ = 22473900. Its totient is φ = 20975584.

The previous prime is 21724739. The next prime is 21724751. The reversal of 21724741 is 14742712.

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 12574116 + 9150625 = 3546^2 + 3025^2 .

It is not a de Polignac number, because 21724741 - 2¹ = 21724739 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 (21724721) 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, 374536 + ... + 374593.

It is an arithmetic number, because the mean of its divisors is an integer number (5618475).

Almost surely, 2^21724741 is an apocalyptic number.

It is an amenable number.

21724741 is a deficient number, since it is larger than the sum of its proper divisors (749159).

21724741 is an equidigital number, since it uses as much as digits as its factorization.

21724741 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 749158.

The product of its digits is 3136, while the sum is 28.

The square root of 21724741 is about 4660.9806907989. The cubic root of 21724741 is about 279.0304091074.

The spelling of 21724741 in words is "twenty-one million, seven hundred twenty-four thousand, seven hundred forty-one".