191508661 has 2 divisors, whose sum is σ = 191508662. Its totient is φ = 191508660.

The previous prime is 191508637. The next prime is 191508677. The reversal of 191508661 is 166805191.

191508661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 177023025 + 14485636 = 13305^2 + 3806^2 .

It is a cyclic number.

It is not a de Polignac number, because 191508661 - 2¹³ = 191500469 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 191508661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191508461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95754330 + 95754331.

It is an arithmetic number, because the mean of its divisors is an integer number (95754331).

Almost surely, 2^191508661 is an apocalyptic number.

It is an amenable number.

191508661 is a deficient number, since it is larger than the sum of its proper divisors (1).

191508661 is an equidigital number, since it uses as much as digits as its factorization.

191508661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 37.

The square root of 191508661 is about 13838.6654342100. The cubic root of 191508661 is about 576.4073011783.

The spelling of 191508661 in words is "one hundred ninety-one million, five hundred eight thousand, six hundred sixty-one".