161721600 has 108 divisors (see below), whose sum is σ = 533778336. Its totient is φ = 43120640.

The previous prime is 161721587. The next prime is 161721617. The reversal of 161721600 is 6127161.

It is a Harshad number since it is a multiple of its sum of digits (24).

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 11 ways as a sum of consecutive naturals, for example, 14989 + ... + 23411.

It is an arithmetic number, because the mean of its divisors is an integer number (4942392).

Almost surely, 2^161721600 is an apocalyptic number.

161721600 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 161721600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (266889168).

161721600 is an abundant number, since it is smaller than the sum of its proper divisors (372056736).

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

161721600 is an equidigital number, since it uses as much as digits as its factorization.

161721600 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8452 (or 8433 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 161721600 is about 12716.9807737529. The cubic root of 161721600 is about 544.8237232560.

Adding to 161721600 its reverse (6127161), we get a palindrome (167848761).

The spelling of 161721600 in words is "one hundred sixty-one million, seven hundred twenty-one thousand, six hundred".