161644261 has 4 divisors (see below), whose sum is σ = 166858624. Its totient is φ = 156429900.

The previous prime is 161644237. The next prime is 161644277. The reversal of 161644261 is 162446161.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 162446161 = 2221 ⋅73141.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161644261 is a prime.

It is a super-2 number, since 2×161644261² = 52257734228472242, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 5214331 = 161644261 / (1 + 6 + 1 + 6 + 4 + 4 + 2 + 6 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161644061) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2607135 + ... + 2607196.

It is an arithmetic number, because the mean of its divisors is an integer number (41714656).

Almost surely, 2^161644261 is an apocalyptic number.

It is an amenable number.

161644261 is a deficient number, since it is larger than the sum of its proper divisors (5214363).

161644261 is an equidigital number, since it uses as much as digits as its factorization.

161644261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5214362.

The product of its digits is 6912, while the sum is 31.

The square root of 161644261 is about 12713.9396333316. The cubic root of 161644261 is about 544.7368603167.

The spelling of 161644261 in words is "one hundred sixty-one million, six hundred forty-four thousand, two hundred sixty-one".