21683909 has 16 divisors (see below), whose sum is σ = 24418800. Its totient is φ = 19117056.

The previous prime is 21683899. The next prime is 21683929. The reversal of 21683909 is 90938612.

It can be written as a sum of positive squares in 8 ways, for example, as 2411809 + 19272100 = 1553^2 + 4390^2 .

It is a cyclic number.

It is not a de Polignac number, because 21683909 - 2¹² = 21679813 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 (21683929) 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, 42347 + ... + 42855.

It is an arithmetic number, because the mean of its divisors is an integer number (1526175).

Almost surely, 2^21683909 is an apocalyptic number.

21683909 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21683909 is a deficient number, since it is larger than the sum of its proper divisors (2734891).

21683909 is a wasteful number, since it uses less digits than its factorization.

21683909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 664.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 21683909 is about 4656.5984366273. The cubic root of 21683909 is about 278.8554854242.

The spelling of 21683909 in words is "twenty-one million, six hundred eighty-three thousand, nine hundred nine".