21166709 has 4 divisors (see below), whose sum is σ = 21333504. Its totient is φ = 20999916.

The previous prime is 21166679. The next prime is 21166711. The reversal of 21166709 is 90766112.

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 21166709 - 2¹² = 21162613 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 (21166799) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 83207 + ... + 83460.

It is an arithmetic number, because the mean of its divisors is an integer number (5333376).

Almost surely, 2^21166709 is an apocalyptic number.

It is an amenable number.

21166709 is a deficient number, since it is larger than the sum of its proper divisors (166795).

21166709 is a wasteful number, since it uses less digits than its factorization.

21166709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166794.

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 21166709 is about 4600.7291813364. The cubic root of 21166709 is about 276.6205537572.

The spelling of 21166709 in words is "twenty-one million, one hundred sixty-six thousand, seven hundred nine".