191601661 has 4 divisors (see below), whose sum is σ = 199932192. Its totient is φ = 183271132.

The previous prime is 191601659. The next prime is 191601677. The reversal of 191601661 is 166106191.

It is a happy number.

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: 166106191 = 151 ⋅1100041.

It is a cyclic number.

It is not a de Polignac number, because 191601661 - 2¹ = 191601659 is a prime.

It is a super-2 number, since 2×191601661² = 73422392995917842, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (191601601) 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, 4165231 + ... + 4165276.

It is an arithmetic number, because the mean of its divisors is an integer number (49983048).

Almost surely, 2^191601661 is an apocalyptic number.

It is an amenable number.

191601661 is a deficient number, since it is larger than the sum of its proper divisors (8330531).

191601661 is an equidigital number, since it uses as much as digits as its factorization.

191601661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8330530.

The product of its (nonzero) digits is 1944, while the sum is 31.

The square root of 191601661 is about 13842.0251769746. The cubic root of 191601661 is about 576.5005906127.

The spelling of 191601661 in words is "one hundred ninety-one million, six hundred one thousand, six hundred sixty-one".