21748513 has 4 divisors (see below), whose sum is σ = 22105108. Its totient is φ = 21391920.

The previous prime is 21748481. The next prime is 21748523. The reversal of 21748513 is 31584712.

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 2634129 + 19114384 = 1623^2 + 4372^2 .

It is a cyclic number.

It is not a de Polignac number, because 21748513 - 2⁵ = 21748481 is a prime.

It is a super-2 number, since 2×21748513² = 945995635422338, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21748523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 178206 + ... + 178327.

It is an arithmetic number, because the mean of its divisors is an integer number (5526277).

Almost surely, 2^21748513 is an apocalyptic number.

It is an amenable number.

21748513 is a deficient number, since it is larger than the sum of its proper divisors (356595).

21748513 is an equidigital number, since it uses as much as digits as its factorization.

21748513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 356594.

The product of its digits is 6720, while the sum is 31.

The square root of 21748513 is about 4663.5301006855. The cubic root of 21748513 is about 279.1321470745.

The spelling of 21748513 in words is "twenty-one million, seven hundred forty-eight thousand, five hundred thirteen".