20217665 has 8 divisors (see below), whose sum is σ = 26127528. Its totient is φ = 14929920.

The previous prime is 20217629. The next prime is 20217677. The reversal of 20217665 is 56671202.

It can be written as a sum of positive squares in 4 ways, for example, as 39601 + 20178064 = 199^2 + 4492^2 .

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

It is not a de Polignac number, because 20217665 - 2⁸ = 20217409 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 155456 + ... + 155585.

It is an arithmetic number, because the mean of its divisors is an integer number (3265941).

Almost surely, 2^20217665 is an apocalyptic number.

It is an amenable number.

20217665 is a deficient number, since it is larger than the sum of its proper divisors (5909863).

20217665 is a wasteful number, since it uses less digits than its factorization.

20217665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 311059.

The product of its (nonzero) digits is 5040, while the sum is 29.

The square root of 20217665 is about 4496.4057868480. The cubic root of 20217665 is about 272.4229336257.

Adding to 20217665 its reverse (56671202), we get a palindrome (76888867).

The spelling of 20217665 in words is "twenty million, two hundred seventeen thousand, six hundred sixty-five".