161644821 has 8 divisors (see below), whose sum is σ = 232105440. Its totient is φ = 99473712.

The previous prime is 161644807. The next prime is 161644829. The reversal of 161644821 is 128446161.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 161644821 - 2¹⁷ = 161513749 is a prime.

It is a super-2 number, since 2×161644821² = 52258096312244082, which contains 22 as substring.

It is a Curzon number.

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, 2072331 + ... + 2072408.

It is an arithmetic number, because the mean of its divisors is an integer number (29013180).

Almost surely, 2^161644821 is an apocalyptic number.

It is an amenable number.

161644821 is a deficient number, since it is larger than the sum of its proper divisors (70460619).

161644821 is a wasteful number, since it uses less digits than its factorization.

161644821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4144755.

The product of its digits is 9216, while the sum is 33.

The square root of 161644821 is about 12713.9616563839. The cubic root of 161644821 is about 544.7374893777.

The spelling of 161644821 in words is "one hundred sixty-one million, six hundred forty-four thousand, eight hundred twenty-one".