21668849 has 4 divisors (see below), whose sum is σ = 21824880. Its totient is φ = 21512820.

The previous prime is 21668839. The next prime is 21668851. The reversal of 21668849 is 94886612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21668849 - 2⁸ = 21668593 is a prime.

It is a Duffinian number.

It is a Curzon 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, 77807 + ... + 78084.

It is an arithmetic number, because the mean of its divisors is an integer number (5456220).

Almost surely, 2^21668849 is an apocalyptic number.

It is an amenable number.

21668849 is a deficient number, since it is larger than the sum of its proper divisors (156031).

21668849 is a wasteful number, since it uses less digits than its factorization.

21668849 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156030.

The product of its digits is 165888, while the sum is 44.

The square root of 21668849 is about 4654.9810955577. The cubic root of 21668849 is about 278.7909131767.

The spelling of 21668849 in words is "twenty-one million, six hundred sixty-eight thousand, eight hundred forty-nine".