21616666 has 8 divisors (see below), whose sum is σ = 32503284. Its totient is φ = 10782240.

The previous prime is 21616657. The next prime is 21616669. The reversal of 21616666 is 66661612.

It can be written as a sum of positive squares in 2 ways, for example, as 21022225 + 594441 = 4585^2 + 771^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21616669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11995 + ... + 13678.

Almost surely, 2^21616666 is an apocalyptic number.

21616666 is a deficient number, since it is larger than the sum of its proper divisors (10886618).

21616666 is a wasteful number, since it uses less digits than its factorization.

21616666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26096.

The product of its digits is 15552, while the sum is 34.

The square root of 21616666 is about 4649.3726458523. The cubic root of 21616666 is about 278.5669381950.

The spelling of 21616666 in words is "twenty-one million, six hundred sixteen thousand, six hundred sixty-six".