161872681 has 2 divisors, whose sum is σ = 161872682. Its totient is φ = 161872680.

The previous prime is 161872679. The next prime is 161872699. The reversal of 161872681 is 186278161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 158357056 + 3515625 = 12584^2 + 1875^2 .

It is a cyclic number.

It is not a de Polignac number, because 161872681 - 2¹ = 161872679 is a prime.

It is a super-2 number, since 2×161872681² = 52405529708255522, which contains 22 as substring.

Together with 161872679, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (161872631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80936340 + 80936341.

It is an arithmetic number, because the mean of its divisors is an integer number (80936341).

Almost surely, 2^161872681 is an apocalyptic number.

It is an amenable number.

161872681 is a deficient number, since it is larger than the sum of its proper divisors (1).

161872681 is an equidigital number, since it uses as much as digits as its factorization.

161872681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32256, while the sum is 40.

The square root of 161872681 is about 12722.9195155829. The cubic root of 161872681 is about 544.9933293238.

The spelling of 161872681 in words is "one hundred sixty-one million, eight hundred seventy-two thousand, six hundred eighty-one".