21666705 has 8 divisors (see below), whose sum is σ = 34666752. Its totient is φ = 11555568.

The previous prime is 21666703. The next prime is 21666709. The reversal of 21666705 is 50766612.

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

It is not a de Polignac number, because 21666705 - 2¹ = 21666703 is a prime.

It is a super-2 number, since 2×21666705² = 938892211114050, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21666703) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 722209 + ... + 722238.

It is an arithmetic number, because the mean of its divisors is an integer number (4333344).

Almost surely, 2^21666705 is an apocalyptic number.

It is an amenable number.

21666705 is a deficient number, since it is larger than the sum of its proper divisors (13000047).

21666705 is a wasteful number, since it uses less digits than its factorization.

21666705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1444455.

The product of its (nonzero) digits is 15120, while the sum is 33.

The square root of 21666705 is about 4654.7507989150. The cubic root of 21666705 is about 278.7817179885.

The spelling of 21666705 in words is "twenty-one million, six hundred sixty-six thousand, seven hundred five".