165312821 has 2 divisors, whose sum is σ = 165312822. Its totient is φ = 165312820.

The previous prime is 165312809. The next prime is 165312859. The reversal of 165312821 is 128213561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 164608900 + 703921 = 12830^2 + 839^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-165312821 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (165312871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82656410 + 82656411.

It is an arithmetic number, because the mean of its divisors is an integer number (82656411).

Almost surely, 2^165312821 is an apocalyptic number.

It is an amenable number.

165312821 is a deficient number, since it is larger than the sum of its proper divisors (1).

165312821 is an equidigital number, since it uses as much as digits as its factorization.

165312821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2880, while the sum is 29.

The square root of 165312821 is about 12857.4033537103. The cubic root of 165312821 is about 548.8270551453.

The spelling of 165312821 in words is "one hundred sixty-five million, three hundred twelve thousand, eight hundred twenty-one".