165551281321 has 2 divisors, whose sum is σ = 165551281322. Its totient is φ = 165551281320.

The previous prime is 165551281267. The next prime is 165551281351. The reversal of 165551281321 is 123182155561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 164340241321 + 1211040000 = 405389^2 + 34800^2 .

It is a cyclic number.

It is not a de Polignac number, because 165551281321 - 2⁹ = 165551280809 is a prime.

It is not a weakly prime, because it can be changed into another prime (165551281351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82775640660 + 82775640661.

It is an arithmetic number, because the mean of its divisors is an integer number (82775640661).

Almost surely, 2^165551281321 is an apocalyptic number.

It is an amenable number.

165551281321 is a deficient number, since it is larger than the sum of its proper divisors (1).

165551281321 is an equidigital number, since it uses as much as digits as its factorization.

165551281321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 72000, while the sum is 40.

The spelling of 165551281321 in words is "one hundred sixty-five billion, five hundred fifty-one million, two hundred eighty-one thousand, three hundred twenty-one".