21666743 has 8 divisors (see below), whose sum is σ = 24810912. Its totient is φ = 18534816.

The previous prime is 21666739. The next prime is 21666761. The reversal of 21666743 is 34766612.

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 21666743 - 2² = 21666739 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21666703) 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, 1121 + ... + 6677.

It is an arithmetic number, because the mean of its divisors is an integer number (3101364).

Almost surely, 2^21666743 is an apocalyptic number.

21666743 is a deficient number, since it is larger than the sum of its proper divisors (3144169).

21666743 is an equidigital number, since it uses as much as digits as its factorization.

21666743 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6121.

The product of its digits is 36288, while the sum is 35.

The square root of 21666743 is about 4654.7548807644. The cubic root of 21666743 is about 278.7818809682.

The spelling of 21666743 in words is "twenty-one million, six hundred sixty-six thousand, seven hundred forty-three".