20191001665 has 16 divisors (see below), whose sum is σ = 24313028688. Its totient is φ = 16096976896.

The previous prime is 20191001659. The next prime is 20191001671. The reversal of 20191001665 is 56610019102.

It is an interprime number because it is at equal distance from previous prime (20191001659) and next prime (20191001671).

It can be written as a sum of positive squares in 8 ways, for example, as 6548481 + 20184453184 = 2559^2 + 142072^2 .

It is a cyclic number.

It is not a de Polignac number, because 20191001665 - 2⁹ = 20191001153 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 15 ways as a sum of consecutive naturals, for example, 4263639 + ... + 4268371.

It is an arithmetic number, because the mean of its divisors is an integer number (1519564293).

Almost surely, 2^20191001665 is an apocalyptic number.

It is an amenable number.

20191001665 is a deficient number, since it is larger than the sum of its proper divisors (4122027023).

20191001665 is a wasteful number, since it uses less digits than its factorization.

20191001665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7508.

The product of its (nonzero) digits is 3240, while the sum is 31.

The spelling of 20191001665 in words is "twenty billion, one hundred ninety-one million, one thousand, six hundred sixty-five".