21671705 has 24 divisors (see below), whose sum is σ = 28929096. Its totient is φ = 15572480.

The previous prime is 21671701. The next prime is 21671731. The reversal of 21671705 is 50717612.

It can be written as a sum of positive squares in 4 ways, for example, as 1628176 + 20043529 = 1276^2 + 4477^2 .

It is not a de Polignac number, because 21671705 - 2² = 21671701 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21671701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 68207 + ... + 68523.

It is an arithmetic number, because the mean of its divisors is an integer number (1205379).

Almost surely, 2^21671705 is an apocalyptic number.

It is an amenable number.

21671705 is a deficient number, since it is larger than the sum of its proper divisors (7257391).

21671705 is a wasteful number, since it uses less digits than its factorization.

21671705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 457 (or 446 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 29.

The square root of 21671705 is about 4655.2878536134. The cubic root of 21671705 is about 278.8031610487.

The spelling of 21671705 in words is "twenty-one million, six hundred seventy-one thousand, seven hundred five".