21703509 has 12 divisors (see below), whose sum is σ = 33193836. Its totient is φ = 13617792.

The previous prime is 21703501. The next prime is 21703541. The reversal of 21703509 is 90530712.

It can be written as a sum of positive squares in 2 ways, for example, as 15563025 + 6140484 = 3945^2 + 2478^2 .

It is not a de Polignac number, because 21703509 - 2³ = 21703501 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21703501) 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 11 ways as a sum of consecutive naturals, for example, 70774 + ... + 71079.

It is an arithmetic number, because the mean of its divisors is an integer number (2766153).

Almost surely, 2^21703509 is an apocalyptic number.

It is an amenable number.

21703509 is a deficient number, since it is larger than the sum of its proper divisors (11490327).

21703509 is a wasteful number, since it uses less digits than its factorization.

21703509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141876 (or 141873 counting only the distinct ones).

The product of its (nonzero) digits is 1890, while the sum is 27.

The square root of 21703509 is about 4658.7025017702. The cubic root of 21703509 is about 278.9394789141.

The spelling of 21703509 in words is "twenty-one million, seven hundred three thousand, five hundred nine".