161644820 has 24 divisors (see below), whose sum is σ = 342573000. Its totient is φ = 64063872.

The previous prime is 161644807. The next prime is 161644829. The reversal of 161644820 is 28446161.

It can be written as a sum of positive squares in 4 ways, for example, as 34316164 + 127328656 = 5858^2 + 11284^2 .

It is a super-2 number, since 2×161644820² = 52258095665664800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161644829) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34895 + ... + 39254.

It is an arithmetic number, because the mean of its divisors is an integer number (14273875).

Almost surely, 2^161644820 is an apocalyptic number.

161644820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161644820 is an abundant number, since it is smaller than the sum of its proper divisors (180928180).

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

161644820 is a wasteful number, since it uses less digits than its factorization.

161644820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74267 (or 74265 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 32.

The square root of 161644820 is about 12713.9616170571. The cubic root of 161644820 is about 544.7374882544.

The spelling of 161644820 in words is "one hundred sixty-one million, six hundred forty-four thousand, eight hundred twenty".