21666315 has 16 divisors (see below), whose sum is σ = 37817856. Its totient is φ = 10504800.

The previous prime is 21666301. The next prime is 21666317. The reversal of 21666315 is 51366612.

It is not a de Polignac number, because 21666315 - 2⁵ = 21666283 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21666317) 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 15 ways as a sum of consecutive naturals, for example, 65491 + ... + 65820.

It is an arithmetic number, because the mean of its divisors is an integer number (2363616).

Almost surely, 2^21666315 is an apocalyptic number.

21666315 is a deficient number, since it is larger than the sum of its proper divisors (16151541).

21666315 is a wasteful number, since it uses less digits than its factorization.

21666315 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131330.

The product of its digits is 6480, while the sum is 30.

The square root of 21666315 is about 4654.7089060434. The cubic root of 21666315 is about 278.7800452911.

The spelling of 21666315 in words is "twenty-one million, six hundred sixty-six thousand, three hundred fifteen".