21166005 has 16 divisors (see below), whose sum is σ = 38703744. Its totient is φ = 9675840.

The previous prime is 21165997. The next prime is 21166007. The reversal of 21166005 is 50066112.

It is a happy number.

It is not a de Polignac number, because 21166005 - 2³ = 21165997 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21166007) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 100686 + ... + 100895.

It is an arithmetic number, because the mean of its divisors is an integer number (2418984).

Almost surely, 2^21166005 is an apocalyptic number.

It is an amenable number.

21166005 is a deficient number, since it is larger than the sum of its proper divisors (17537739).

21166005 is a wasteful number, since it uses less digits than its factorization.

21166005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 201596.

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 21166005 is about 4600.6526710892. The cubic root of 21166005 is about 276.6174869440.

The spelling of 21166005 in words is "twenty-one million, one hundred sixty-six thousand, five".