165561811 has 2 divisors, whose sum is σ = 165561812. Its totient is φ = 165561810.

The previous prime is 165561787. The next prime is 165561821. The reversal of 165561811 is 118165561.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 165561811 - 2⁵ = 165561779 is a prime.

It is not a weakly prime, because it can be changed into another prime (165561821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82780905 + 82780906.

It is an arithmetic number, because the mean of its divisors is an integer number (82780906).

Almost surely, 2^165561811 is an apocalyptic number.

165561811 is a deficient number, since it is larger than the sum of its proper divisors (1).

165561811 is an equidigital number, since it uses as much as digits as its factorization.

165561811 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7200, while the sum is 34.

The square root of 165561811 is about 12867.0824587394. The cubic root of 165561811 is about 549.1024600766.

The spelling of 165561811 in words is "one hundred sixty-five million, five hundred sixty-one thousand, eight hundred eleven".