665734681920 has 1344 divisors, whose sum is σ = 2799879340032. Its totient is φ = 133872076800.

The previous prime is 665734681891. The next prime is 665734681939. The reversal of 665734681920 is 29186437566.

It is a tau number, because it is divible by the number of its divisors (1344).

It is a super-2 number, since 2×665734681920² (a number of 24 digits) contains 22 as substring.

It is a congruent 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 191 ways as a sum of consecutive naturals, for example, 21475312305 + ... + 21475312335.

It is a 1-persistent number, because it is pandigital, but 2⋅665734681920 = 1331469363840 is not.

Almost surely, 2^665734681920 is an apocalyptic number.

665734681920 is a gapful number since it is divisible by the number (60) 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 665734681920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1399939670016).

665734681920 is an abundant number, since it is smaller than the sum of its proper divisors (2134144658112).

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

665734681920 is an frugal number, since it uses more digits than its factorization.

665734681920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119 (or 59 counting only the distinct ones).

The product of its (nonzero) digits is 13063680, while the sum is 57.

The spelling of 665734681920 in words is "six hundred sixty-five billion, seven hundred thirty-four million, six hundred eighty-one thousand, nine hundred twenty".