165456721 has 2 divisors, whose sum is σ = 165456722. Its totient is φ = 165456720.

The previous prime is 165456713. The next prime is 165456749. The reversal of 165456721 is 127654561.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 83010321 + 82446400 = 9111^2 + 9080^2 .

It is a cyclic number.

It is not a de Polignac number, because 165456721 - 2³ = 165456713 is a prime.

It is a Chen prime.

It is an alternating number because its digits alternate between odd and even.

It is not a weakly prime, because it can be changed into another prime (165456761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82728360 + 82728361.

It is an arithmetic number, because the mean of its divisors is an integer number (82728361).

Almost surely, 2^165456721 is an apocalyptic number.

It is an amenable number.

165456721 is a deficient number, since it is larger than the sum of its proper divisors (1).

165456721 is an equidigital number, since it uses as much as digits as its factorization.

165456721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 50400, while the sum is 37.

The square root of 165456721 is about 12862.9981341832. The cubic root of 165456721 is about 548.9862549547.

The spelling of 165456721 in words is "one hundred sixty-five million, four hundred fifty-six thousand, seven hundred twenty-one".