21159909 has 6 divisors (see below), whose sum is σ = 30564326. Its totient is φ = 14106600.

The previous prime is 21159907. The next prime is 21159911. The reversal of 21159909 is 90995112.

It is an interprime number because it is at equal distance from previous prime (21159907) and next prime (21159911).

It can be written as a sum of positive squares in only one way, i.e., 21068100 + 91809 = 4590^2 + 303^2 .

It is not a de Polignac number, because 21159909 - 2¹ = 21159907 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21159907) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1175542 + ... + 1175559.

Almost surely, 2^21159909 is an apocalyptic number.

It is an amenable number.

21159909 is a deficient number, since it is larger than the sum of its proper divisors (9404417).

21159909 is a wasteful number, since it uses less digits than its factorization.

21159909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2351107 (or 2351104 counting only the distinct ones).

The product of its (nonzero) digits is 7290, while the sum is 36.

The square root of 21159909 is about 4599.9901086850. The cubic root of 21159909 is about 276.5909282852.

The spelling of 21159909 in words is "twenty-one million, one hundred fifty-nine thousand, nine hundred nine".