21650665 has 8 divisors (see below), whose sum is σ = 26614728. Its totient is φ = 16897920.

The previous prime is 21650653. The next prime is 21650683. The reversal of 21650665 is 56605612.

It can be written as a sum of positive squares in 4 ways, for example, as 1075369 + 20575296 = 1037^2 + 4536^2 .

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

It is a de Polignac number, because none of the positive numbers 2^k-21650665 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, 52602 + ... + 53011.

It is an arithmetic number, because the mean of its divisors is an integer number (3326841).

Almost surely, 2^21650665 is an apocalyptic number.

It is an amenable number.

21650665 is a deficient number, since it is larger than the sum of its proper divisors (4964063).

21650665 is a wasteful number, since it uses less digits than its factorization.

21650665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105659.

The product of its (nonzero) digits is 10800, while the sum is 31.

The square root of 21650665 is about 4653.0275090526. The cubic root of 21650665 is about 278.7129063768.

The spelling of 21650665 in words is "twenty-one million, six hundred fifty thousand, six hundred sixty-five".