161121900 has 144 divisors (see below), whose sum is σ = 512467200. Its totient is φ = 38903040.

The previous prime is 161121899. The next prime is 161121901. The reversal of 161121900 is 9121161.

It is an interprime number because it is at equal distance from previous prime (161121899) and next prime (161121901).

It is a super-2 number, since 2×161121900² = 51920533319220000, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (161121901) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 130486 + ... + 131714.

It is an arithmetic number, because the mean of its divisors is an integer number (3558800).

Almost surely, 2^161121900 is an apocalyptic number.

161121900 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 161121900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (256233600).

161121900 is an abundant number, since it is smaller than the sum of its proper divisors (351345300).

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

161121900 is a wasteful number, since it uses less digits than its factorization.

161121900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1288 (or 1281 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 21.

The square root of 161121900 is about 12693.3801644794. The cubic root of 161121900 is about 544.1494462173.

The spelling of 161121900 in words is "one hundred sixty-one million, one hundred twenty-one thousand, nine hundred".