21757705 has 8 divisors (see below), whose sum is σ = 27645192. Its totient is φ = 16382208.

The previous prime is 21757693. The next prime is 21757709. The reversal of 21757705 is 50775712.

It can be written as a sum of positive squares in 4 ways, for example, as 9834496 + 11923209 = 3136^2 + 3453^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21757705 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21757709) 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, 127902 + ... + 128071.

It is an arithmetic number, because the mean of its divisors is an integer number (3455649).

Almost surely, 2^21757705 is an apocalyptic number.

It is an amenable number.

21757705 is a deficient number, since it is larger than the sum of its proper divisors (5887487).

21757705 is a wasteful number, since it uses less digits than its factorization.

21757705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 255995.

The product of its (nonzero) digits is 17150, while the sum is 34.

The square root of 21757705 is about 4664.5155161067. The cubic root of 21757705 is about 279.1714665643.

The spelling of 21757705 in words is "twenty-one million, seven hundred fifty-seven thousand, seven hundred five".