1981647565 has 8 divisors (see below), whose sum is σ = 2454686208. Its totient is φ = 1534178640.

The previous prime is 1981647557. The next prime is 1981647589. The reversal of 1981647565 is 5657461891.

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

It is not a de Polignac number, because 1981647565 - 2³ = 1981647557 is a prime.

It is a Duffinian number.

It is a congruent 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, 6392257 + ... + 6392566.

It is an arithmetic number, because the mean of its divisors is an integer number (306835776).

Almost surely, 2^1981647565 is an apocalyptic number.

It is an amenable number.

1981647565 is a deficient number, since it is larger than the sum of its proper divisors (473038643).

1981647565 is a wasteful number, since it uses less digits than its factorization.

1981647565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12784859.

The product of its digits is 1814400, while the sum is 52.

The square root of 1981647565 is about 44515.7002079042. The cubic root of 1981647565 is about 1256.0554318933.

The spelling of 1981647565 in words is "one billion, nine hundred eighty-one million, six hundred forty-seven thousand, five hundred sixty-five".