21745447 has 4 divisors (see below), whose sum is σ = 22495320. Its totient is φ = 20995576.

The previous prime is 21745441. The next prime is 21745469. The reversal of 21745447 is 74454712.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21745447 - 2²³ = 13356839 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 (21745441) 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, 374893 + ... + 374950.

It is an arithmetic number, because the mean of its divisors is an integer number (5623830).

Almost surely, 2^21745447 is an apocalyptic number.

21745447 is a deficient number, since it is larger than the sum of its proper divisors (749873).

21745447 is an equidigital number, since it uses as much as digits as its factorization.

21745447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 749872.

The product of its digits is 31360, while the sum is 34.

The square root of 21745447 is about 4663.2013681590. The cubic root of 21745447 is about 279.1190295588.

The spelling of 21745447 in words is "twenty-one million, seven hundred forty-five thousand, four hundred forty-seven".