165861761 has 4 divisors (see below), whose sum is σ = 178620372. Its totient is φ = 153103152.

The previous prime is 165861737. The next prime is 165861779. The reversal of 165861761 is 167168561.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 97634161 + 68227600 = 9881^2 + 8260^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-165861761 is a prime.

It is a super-2 number, since 2×165861761² = 55020247524042242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165861721) 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, 6379286 + ... + 6379311.

It is an arithmetic number, because the mean of its divisors is an integer number (44655093).

Almost surely, 2^165861761 is an apocalyptic number.

It is an amenable number.

165861761 is a deficient number, since it is larger than the sum of its proper divisors (12758611).

165861761 is a wasteful number, since it uses less digits than its factorization.

165861761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12758610.

The product of its digits is 60480, while the sum is 41.

The square root of 165861761 is about 12878.7328957472. The cubic root of 165861761 is about 549.4338648392.

The spelling of 165861761 in words is "one hundred sixty-five million, eight hundred sixty-one thousand, seven hundred sixty-one".