21949565665 has 8 divisors (see below), whose sum is σ = 26358559848. Its totient is φ = 17546931840.

The previous prime is 21949565639. The next prime is 21949565711. The reversal of 21949565665 is 56656594912.

It can be written as a sum of positive squares in 4 ways, for example, as 6610990864 + 15338574801 = 81308^2 + 123849^2 .

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

It is not a de Polignac number, because 21949565665 - 2⁵ = 21949565633 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 (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1582492 + ... + 1596301.

It is an arithmetic number, because the mean of its divisors is an integer number (3294819981).

Almost surely, 2^21949565665 is an apocalyptic number.

It is an amenable number.

21949565665 is a deficient number, since it is larger than the sum of its proper divisors (4408994183).

21949565665 is a wasteful number, since it uses less digits than its factorization.

21949565665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3180179.

The product of its digits is 17496000, while the sum is 58.

The spelling of 21949565665 in words is "twenty-one billion, nine hundred forty-nine million, five hundred sixty-five thousand, six hundred sixty-five".