166561920 has 512 divisors, whose sum is σ = 722649600. Its totient is φ = 35831808.

The previous prime is 166561873. The next prime is 166561939. The reversal of 166561920 is 29165661.

166561920 is a `hidden beast` number, since 1 + 6 + 6 + 561 + 92 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 9797752 + ... + 9797768.

It is an arithmetic number, because the mean of its divisors is an integer number (1411425).

Almost surely, 2^166561920 is an apocalyptic number.

166561920 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 166561920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (361324800).

166561920 is an abundant number, since it is smaller than the sum of its proper divisors (556087680).

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

166561920 is an frugal number, since it uses more digits than its factorization.

166561920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64 (or 34 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 166561920 is about 12905.8870287943. The cubic root of 166561920 is about 550.2058953642.

The spelling of 166561920 in words is "one hundred sixty-six million, five hundred sixty-one thousand, nine hundred twenty".