21660905 has 8 divisors (see below), whose sum is σ = 29706432. Its totient is φ = 14853168.

The previous prime is 21660901. The next prime is 21660923. The reversal of 21660905 is 50906612.

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

It is a cyclic number.

It is not a de Polignac number, because 21660905 - 2² = 21660901 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21660901) 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 7 ways as a sum of consecutive naturals, for example, 309407 + ... + 309476.

It is an arithmetic number, because the mean of its divisors is an integer number (3713304).

Almost surely, 2^21660905 is an apocalyptic number.

It is an amenable number.

21660905 is a deficient number, since it is larger than the sum of its proper divisors (8045527).

21660905 is an equidigital number, since it uses as much as digits as its factorization.

21660905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 618895.

The product of its (nonzero) digits is 3240, while the sum is 29.

The square root of 21660905 is about 4654.1277378259. The cubic root of 21660905 is about 278.7568399054.

The spelling of 21660905 in words is "twenty-one million, six hundred sixty thousand, nine hundred five".