165721920 has 336 divisors, whose sum is σ = 661586688. Its totient is φ = 34836480.

The previous prime is 165721903. The next prime is 165721951. The reversal of 165721920 is 29127561.

165721920 = T₃₇₉ + T₃₈₀ + ... + T₁₀₁₅.

It is a tau number, because it is divible by the number of its divisors (336).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 611385 + ... + 611655.

It is an arithmetic number, because the mean of its divisors is an integer number (1969008).

Almost surely, 2^165721920 is an apocalyptic number.

165721920 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 165721920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (330793344).

165721920 is an abundant number, since it is smaller than the sum of its proper divisors (495864768).

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

165721920 is a wasteful number, since it uses less digits than its factorization.

165721920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318 (or 301 counting only the distinct ones).

The product of its (nonzero) digits is 7560, while the sum is 33.

The square root of 165721920 is about 12873.3026065575. The cubic root of 165721920 is about 549.2794089358.

The spelling of 165721920 in words is "one hundred sixty-five million, seven hundred twenty-one thousand, nine hundred twenty".