21207166 has 4 divisors (see below), whose sum is σ = 31810752. Its totient is φ = 10603582.

The previous prime is 21207161. The next prime is 21207167. The reversal of 21207166 is 66170212.

It is a semiprime because it is the product of two primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21207166.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21207161) 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 as a sum of consecutive naturals, namely, 5301790 + ... + 5301793.

It is an arithmetic number, because the mean of its divisors is an integer number (7952688).

Almost surely, 2^21207166 is an apocalyptic number.

21207166 is a deficient number, since it is larger than the sum of its proper divisors (10603586).

21207166 is a wasteful number, since it uses less digits than its factorization.

21207166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10603585.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21207166 is about 4605.1238854129. The cubic root of 21207166 is about 276.7966812030.

Adding to 21207166 its reverse (66170212), we get a palindrome (87377378).

The spelling of 21207166 in words is "twenty-one million, two hundred seven thousand, one hundred sixty-six".