21726745 has 4 divisors (see below), whose sum is σ = 26072100. Its totient is φ = 17381392.

The previous prime is 21726721. The next prime is 21726791. The reversal of 21726745 is 54762712.

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 3655744 + 18071001 = 1912^2 + 4251^2 .

It is a cyclic number.

It is not a de Polignac number, because 21726745 - 2⁹ = 21726233 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21726745.

It is an unprimeable number.

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, 2172670 + ... + 2172679.

It is an arithmetic number, because the mean of its divisors is an integer number (6518025).

Almost surely, 2^21726745 is an apocalyptic number.

It is an amenable number.

21726745 is a deficient number, since it is larger than the sum of its proper divisors (4345355).

21726745 is an equidigital number, since it uses as much as digits as its factorization.

21726745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4345354.

The product of its digits is 23520, while the sum is 34.

The square root of 21726745 is about 4661.1956620593. The cubic root of 21726745 is about 279.0389885690.

It can be divided in two parts, 217 and 26745, that added together give a palindrome (26962).

The spelling of 21726745 in words is "twenty-one million, seven hundred twenty-six thousand, seven hundred forty-five".