21665743 has 8 divisors (see below), whose sum is σ = 23960016. Its totient is φ = 19425600.

The previous prime is 21665737. The next prime is 21665767. The reversal of 21665743 is 34756612.

It is a happy number.

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 21665743 - 2¹³ = 21657551 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21665699 and 21665708.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21665713) 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, 12688 + ... + 14293.

It is an arithmetic number, because the mean of its divisors is an integer number (2995002).

Almost surely, 2^21665743 is an apocalyptic number.

21665743 is a deficient number, since it is larger than the sum of its proper divisors (2294273).

21665743 is a wasteful number, since it uses less digits than its factorization.

21665743 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27065.

The product of its digits is 30240, while the sum is 34.

The square root of 21665743 is about 4654.6474624831. The cubic root of 21665743 is about 278.7775919653. Note that the first 3 decimals are identical.

The spelling of 21665743 in words is "twenty-one million, six hundred sixty-five thousand, seven hundred forty-three".