66665405520 has 720 divisors, whose sum is σ = 268737545232. Its totient is φ = 14760345600.

The previous prime is 66665405473. The next prime is 66665405549. The reversal of 66665405520 is 2550456666.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 5426974224 + 61238431296 = 73668^2 + 247464^2 .

It is a tau number, because it is divible by the number of its divisors (720).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 188853664 + ... + 188854016.

Almost surely, 2^66665405520 is an apocalyptic number.

66665405520 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 66665405520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (134368772616).

66665405520 is an abundant number, since it is smaller than the sum of its proper divisors (202072139712).

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

66665405520 is a wasteful number, since it uses less digits than its factorization.

66665405520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 540 (or 524 counting only the distinct ones).

The product of its (nonzero) digits is 1296000, while the sum is 45.

The spelling of 66665405520 in words is "sixty-six billion, six hundred sixty-five million, four hundred five thousand, five hundred twenty".