164238721 has 2 divisors, whose sum is σ = 164238722. Its totient is φ = 164238720.

The previous prime is 164238707. The next prime is 164238733. The reversal of 164238721 is 127832461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 159744321 + 4494400 = 12639^2 + 2120^2 .

It is an emirp because it is prime and its reverse (127832461) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 164238721 - 2⁵ = 164238689 is a prime.

It is not a weakly prime, because it can be changed into another prime (164238121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82119360 + 82119361.

It is an arithmetic number, because the mean of its divisors is an integer number (82119361).

Almost surely, 2^164238721 is an apocalyptic number.

It is an amenable number.

164238721 is a deficient number, since it is larger than the sum of its proper divisors (1).

164238721 is an equidigital number, since it uses as much as digits as its factorization.

164238721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16128, while the sum is 34.

The square root of 164238721 is about 12815.5655747220. The cubic root of 164238721 is about 547.6358257146.

The spelling of 164238721 in words is "one hundred sixty-four million, two hundred thirty-eight thousand, seven hundred twenty-one".