21709943 has 8 divisors (see below), whose sum is σ = 22173168. Its totient is φ = 21250944.

The previous prime is 21709939. The next prime is 21709949. The reversal of 21709943 is 34990712.

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 21709943 - 2² = 21709939 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21709949) 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 7 ways as a sum of consecutive naturals, for example, 10655 + ... + 12527.

It is an arithmetic number, because the mean of its divisors is an integer number (2771646).

Almost surely, 2^21709943 is an apocalyptic number.

21709943 is a deficient number, since it is larger than the sum of its proper divisors (463225).

21709943 is a wasteful number, since it uses less digits than its factorization.

21709943 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2113.

The product of its (nonzero) digits is 13608, while the sum is 35.

The square root of 21709943 is about 4659.3929862161. The cubic root of 21709943 is about 278.9670400378.

The spelling of 21709943 in words is "twenty-one million, seven hundred nine thousand, nine hundred forty-three".