21740509 has 4 divisors (see below), whose sum is σ = 24846304. Its totient is φ = 18634716.

The previous prime is 21740491. The next prime is 21740533. The reversal of 21740509 is 90504712.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21740509 - 2¹³ = 21732317 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21740539) 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 3 ways as a sum of consecutive naturals, for example, 1552887 + ... + 1552900.

It is an arithmetic number, because the mean of its divisors is an integer number (6211576).

Almost surely, 2^21740509 is an apocalyptic number.

It is an amenable number.

21740509 is a deficient number, since it is larger than the sum of its proper divisors (3105795).

21740509 is an equidigital number, since it uses as much as digits as its factorization.

21740509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3105794.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21740509 is about 4662.6718735077. The cubic root of 21740509 is about 279.0979003218.

The spelling of 21740509 in words is "twenty-one million, seven hundred forty thousand, five hundred nine".