21166667 has 4 divisors (see below), whose sum is σ = 21207816. Its totient is φ = 21125520.

The previous prime is 21166643. The next prime is 21166679. The reversal of 21166667 is 76666112.

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

It is a cyclic number.

It is not a de Polignac number, because 21166667 - 2²² = 16972363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21166367) 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 3 ways as a sum of consecutive naturals, for example, 19793 + ... + 20834.

It is an arithmetic number, because the mean of its divisors is an integer number (5301954).

Almost surely, 2^21166667 is an apocalyptic number.

21166667 is a deficient number, since it is larger than the sum of its proper divisors (41149).

21166667 is an equidigital number, since it uses as much as digits as its factorization.

21166667 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41148.

The product of its digits is 18144, while the sum is 35.

The square root of 21166667 is about 4600.7246168403. The cubic root of 21166667 is about 276.6203707958.

The spelling of 21166667 in words is "twenty-one million, one hundred sixty-six thousand, six hundred sixty-seven".