21753909 has 24 divisors (see below), whose sum is σ = 32794112. Its totient is φ = 13880160.

The previous prime is 21753887. The next prime is 21753911. The reversal of 21753909 is 90935712.

It is not a de Polignac number, because 21753909 - 2⁵ = 21753877 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 (21753989) 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 23 ways as a sum of consecutive naturals, for example, 28359 + ... + 29115.

Almost surely, 2^21753909 is an apocalyptic number.

It is an amenable number.

21753909 is a deficient number, since it is larger than the sum of its proper divisors (11040203).

21753909 is a wasteful number, since it uses less digits than its factorization.

21753909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 897 (or 894 counting only the distinct ones).

The product of its (nonzero) digits is 17010, while the sum is 36.

The square root of 21753909 is about 4664.1085965059. The cubic root of 21753909 is about 279.1552302238.

It can be divided in two parts, 2175 and 3909, that added together give a square (6084 = 78²).

The spelling of 21753909 in words is "twenty-one million, seven hundred fifty-three thousand, nine hundred nine".