21072166 has 8 divisors (see below), whose sum is σ = 32462640. Its totient is φ = 10251288.

The previous prime is 21072137. The next prime is 21072169. The reversal of 21072166 is 66127012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21072166.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21072169) 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, 142306 + ... + 142453.

It is an arithmetic number, because the mean of its divisors is an integer number (4057830).

Almost surely, 2^21072166 is an apocalyptic number.

21072166 is a deficient number, since it is larger than the sum of its proper divisors (11390474).

21072166 is a wasteful number, since it uses less digits than its factorization.

21072166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 284798.

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

The square root of 21072166 is about 4590.4428980219. The cubic root of 21072166 is about 276.2080888896.

Adding to 21072166 its reverse (66127012), we get a palindrome (87199178).

The spelling of 21072166 in words is "twenty-one million, seventy-two thousand, one hundred sixty-six".