165621400 has 96 divisors (see below), whose sum is σ = 442694880. Its totient is φ = 56448000.

The previous prime is 165621371. The next prime is 165621403. The reversal of 165621400 is 4126561.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165621403) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 393190 + ... + 393610.

It is an arithmetic number, because the mean of its divisors is an integer number (4611405).

Almost surely, 2^165621400 is an apocalyptic number.

165621400 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 165621400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (221347440).

165621400 is an abundant number, since it is smaller than the sum of its proper divisors (277073480).

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

165621400 is a wasteful number, since it uses less digits than its factorization.

165621400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 725 (or 716 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 165621400 is about 12869.3978103095. The cubic root of 165621400 is about 549.1683298193.

Adding to 165621400 its reverse (4126561), we get a palindrome (169747961).

The spelling of 165621400 in words is "one hundred sixty-five million, six hundred twenty-one thousand, four hundred".