166378355581 has 32 divisors (see below), whose sum is σ = 189442084608. Its totient is φ = 145233792000.

The previous prime is 166378355567. The next prime is 166378355603. The reversal of 166378355581 is 185553873661.

It is a cyclic number.

It is not a de Polignac number, because 166378355581 - 2⁷ = 166378355453 is a prime.

It is a super-2 number, since 2×166378355581² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (166378355681) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4219206 + ... + 4258456.

It is an arithmetic number, because the mean of its divisors is an integer number (5920065144).

Almost surely, 2^166378355581 is an apocalyptic number.

It is an amenable number.

166378355581 is a deficient number, since it is larger than the sum of its proper divisors (23063729027).

166378355581 is a wasteful number, since it uses less digits than its factorization.

166378355581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39621.

The product of its digits is 18144000, while the sum is 58.

The spelling of 166378355581 in words is "one hundred sixty-six billion, three hundred seventy-eight million, three hundred fifty-five thousand, five hundred eighty-one".