165781907 has 4 divisors (see below), whose sum is σ = 172989840. Its totient is φ = 158573976.

The previous prime is 165781879. The next prime is 165781927. The reversal of 165781907 is 709187561.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 709187561 = 661 ⋅1072901.

It is a cyclic number.

It is not a de Polignac number, because 165781907 - 2¹⁶ = 165716371 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165781927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3603932 + ... + 3603977.

It is an arithmetic number, because the mean of its divisors is an integer number (43247460).

Almost surely, 2^165781907 is an apocalyptic number.

165781907 is a deficient number, since it is larger than the sum of its proper divisors (7207933).

165781907 is an equidigital number, since it uses as much as digits as its factorization.

165781907 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7207932.

The product of its (nonzero) digits is 105840, while the sum is 44.

The square root of 165781907 is about 12875.6322951535. The cubic root of 165781907 is about 549.3456758667.

The spelling of 165781907 in words is "one hundred sixty-five million, seven hundred eighty-one thousand, nine hundred seven".