165661251840 has 1440 divisors, whose sum is σ = 743634017280. Its totient is φ = 34334834688.

The previous prime is 165661251839. The next prime is 165661251859. The reversal of 165661251840 is 48152166561.

165661251840 is a `hidden beast` number, since 1 + 6 + 566 + 1 + 2 + 5 + 1 + 84 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (1440).

It is a super-2 number, since 2×165661251840² (a number of 23 digits) contains 22 as substring.

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

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 159 ways as a sum of consecutive naturals, for example, 357799449 + ... + 357799911.

It is an arithmetic number, because the mean of its divisors is an integer number (516412512).

Almost surely, 2^165661251840 is an apocalyptic number.

165661251840 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 165661251840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (371817008640).

165661251840 is an abundant number, since it is smaller than the sum of its proper divisors (577972765440).

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

165661251840 is a wasteful number, since it uses less digits than its factorization.

165661251840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 549 (or 526 counting only the distinct ones).

The product of its (nonzero) digits is 345600, while the sum is 45.

The spelling of 165661251840 in words is "one hundred sixty-five billion, six hundred sixty-one million, two hundred fifty-one thousand, eight hundred forty".