21745623 has 8 divisors (see below), whose sum is σ = 29016688. Its totient is φ = 14485824.

The previous prime is 21745613. The next prime is 21745627. The reversal of 21745623 is 32654712.

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

It is not a de Polignac number, because 21745623 - 2¹⁰ = 21744599 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 (21745627) 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, 4161 + ... + 7797.

It is an arithmetic number, because the mean of its divisors is an integer number (3627086).

Almost surely, 2^21745623 is an apocalyptic number.

21745623 is a deficient number, since it is larger than the sum of its proper divisors (7271065).

21745623 is a wasteful number, since it uses less digits than its factorization.

21745623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5633.

The product of its digits is 10080, while the sum is 30.

The square root of 21745623 is about 4663.2202392767. The cubic root of 21745623 is about 279.1197825872.

The spelling of 21745623 in words is "twenty-one million, seven hundred forty-five thousand, six hundred twenty-three".