21666793 has 8 divisors (see below), whose sum is σ = 22485512. Its totient is φ = 20860416.

The previous prime is 21666791. The next prime is 21666811. The reversal of 21666793 is 39766612.

It can be written as a sum of positive squares in 4 ways, for example, as 3790809 + 17875984 = 1947^2 + 4228^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21666793 - 2¹ = 21666791 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21666791) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 571 + ... + 6607.

It is an arithmetic number, because the mean of its divisors is an integer number (2810689).

Almost surely, 2^21666793 is an apocalyptic number.

It is an amenable number.

21666793 is a deficient number, since it is larger than the sum of its proper divisors (818719).

21666793 is an equidigital number, since it uses as much as digits as its factorization.

21666793 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6171.

The product of its digits is 81648, while the sum is 40.

The square root of 21666793 is about 4654.7602516134. The cubic root of 21666793 is about 278.7820954149.

The spelling of 21666793 in words is "twenty-one million, six hundred sixty-six thousand, seven hundred ninety-three".