165665904640 has 96 divisors (see below), whose sum is σ = 410324503680. Its totient is φ = 64128614400.

The previous prime is 165665904631. The next prime is 165665904647. The reversal of 165665904640 is 46409566561.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165665904647) by changing a digit.

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, 56500 + ... + 578380.

It is an arithmetic number, because the mean of its divisors is an integer number (4274213580).

Almost surely, 2^165665904640 is an apocalyptic number.

165665904640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 165665904640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (205162251840).

165665904640 is an abundant number, since it is smaller than the sum of its proper divisors (244658599040).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

165665904640 is an equidigital number, since it uses as much as digits as its factorization.

165665904640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 521939 (or 521919 counting only the distinct ones).

The product of its (nonzero) digits is 4665600, while the sum is 52.

The spelling of 165665904640 in words is "one hundred sixty-five billion, six hundred sixty-five million, nine hundred four thousand, six hundred forty".