21668837 has 4 divisors (see below), whose sum is σ = 21723276. Its totient is φ = 21614400.

The previous prime is 21668827. The next prime is 21668839. The reversal of 21668837 is 73886612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 21104836 + 564001 = 4594^2 + 751^2 .

It is a cyclic number.

It is not a de Polignac number, because 21668837 - 2¹⁰ = 21667813 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21668794 and 21668803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21668839) 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 3 ways as a sum of consecutive naturals, for example, 26618 + ... + 27419.

It is an arithmetic number, because the mean of its divisors is an integer number (5430819).

Almost surely, 2^21668837 is an apocalyptic number.

It is an amenable number.

21668837 is a deficient number, since it is larger than the sum of its proper divisors (54439).

21668837 is an equidigital number, since it uses as much as digits as its factorization.

21668837 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54438.

The product of its digits is 96768, while the sum is 41.

The square root of 21668837 is about 4654.9798066157. The cubic root of 21668837 is about 278.7908617128.

The spelling of 21668837 in words is "twenty-one million, six hundred sixty-eight thousand, eight hundred thirty-seven".