21447745 has 16 divisors (see below), whose sum is σ = 28677888. Its totient is φ = 15264640.

The previous prime is 21447743. The next prime is 21447749. The reversal of 21447745 is 54774412.

It is a happy number.

It is not a de Polignac number, because 21447745 - 2¹ = 21447743 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21447745.

It is not an unprimeable number, because it can be changed into a prime (21447743) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1564 + ... + 6733.

It is an arithmetic number, because the mean of its divisors is an integer number (1792368).

Almost surely, 2^21447745 is an apocalyptic number.

It is an amenable number.

21447745 is a deficient number, since it is larger than the sum of its proper divisors (7230143).

21447745 is a wasteful number, since it uses less digits than its factorization.

21447745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8360.

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

The square root of 21447745 is about 4631.1710182199. The cubic root of 21447745 is about 277.8394299006.

It can be divided in two parts, 2144 and 7745, that added together give a palindrome (9889).

The spelling of 21447745 in words is "twenty-one million, four hundred forty-seven thousand, seven hundred forty-five".