165861810 has 64 divisors (see below), whose sum is σ = 453116160. Its totient is φ = 43148160.

The previous prime is 165861799. The next prime is 165861833. The reversal of 165861810 is 18168561.

It is a super-2 number, since 2×165861810² = 55020280032952200, which contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3579 + ... + 18561.

It is an arithmetic number, because the mean of its divisors is an integer number (7079940).

Almost surely, 2^165861810 is an apocalyptic number.

165861810 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 165861810, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (226558080).

165861810 is an abundant number, since it is smaller than the sum of its proper divisors (287254350).

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

165861810 is a wasteful number, since it uses less digits than its factorization.

165861810 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15040 (or 15034 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The square root of 165861810 is about 12878.7347981081. The cubic root of 165861810 is about 549.4339189450.

The spelling of 165861810 in words is "one hundred sixty-five million, eight hundred sixty-one thousand, eight hundred ten".