161961658 has 4 divisors (see below), whose sum is σ = 242942490. Its totient is φ = 80980828.

The previous prime is 161961641. The next prime is 161961673. The reversal of 161961658 is 856169161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 856169161 = 389 ⋅2200949.

It can be written as a sum of positive squares in only one way, i.e., 156425049 + 5536609 = 12507^2 + 2353^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40490413 + ... + 40490416.

Almost surely, 2^161961658 is an apocalyptic number.

161961658 is a deficient number, since it is larger than the sum of its proper divisors (80980832).

161961658 is an equidigital number, since it uses as much as digits as its factorization.

161961658 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80980831.

The product of its digits is 77760, while the sum is 43.

The square root of 161961658 is about 12726.4157562135. The cubic root of 161961658 is about 545.0931670255.

The spelling of 161961658 in words is "one hundred sixty-one million, nine hundred sixty-one thousand, six hundred fifty-eight".