166521403534640 has 320 divisors, whose sum is σ = 508132231741440. Its totient is φ = 49168013368320.

The previous prime is 166521403534631. The next prime is 166521403534693. The reversal of 166521403534640 is 46435304125661.

It is a happy number.

166521403534640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2505442049 + ... + 2505508511.

It is an arithmetic number, because the mean of its divisors is an integer number (1587913224192).

Almost surely, 2^{166521403534640} is an apocalyptic number.

166521403534640 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 166521403534640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (254066115870720).

166521403534640 is an abundant number, since it is smaller than the sum of its proper divisors (341610828206800).

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

166521403534640 is a wasteful number, since it uses less digits than its factorization.

166521403534640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87920 (or 87914 counting only the distinct ones).

The product of its (nonzero) digits is 6220800, while the sum is 50.

The spelling of 166521403534640 in words is "one hundred sixty-six trillion, five hundred twenty-one billion, four hundred three million, five hundred thirty-four thousand, six hundred forty".