171640991 has 2 divisors, whose sum is σ = 171640992. Its totient is φ = 171640990.

The previous prime is 171640979. The next prime is 171640999. The reversal of 171640991 is 199046171.

171640991 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 is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-171640991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (171640999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 85820495 + 85820496.

It is an arithmetic number, because the mean of its divisors is an integer number (85820496).

Almost surely, 2^171640991 is an apocalyptic number.

171640991 is a deficient number, since it is larger than the sum of its proper divisors (1).

171640991 is an equidigital number, since it uses as much as digits as its factorization.

171640991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13608, while the sum is 38.

The square root of 171640991 is about 13101.1828091970. The cubic root of 171640991 is about 555.7425776842.

The spelling of 171640991 in words is "one hundred seventy-one million, six hundred forty thousand, nine hundred ninety-one".