718138921 has 2 divisors, whose sum is σ = 718138922. Its totient is φ = 718138920.

The previous prime is 718138907. The next prime is 718138931. The reversal of 718138921 is 129831817.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 699338025 + 18800896 = 26445^2 + 4336^2 .

It is an emirp because it is prime and its reverse (129831817) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 718138921 - 2⁹ = 718138409 is a prime.

It is not a weakly prime, because it can be changed into another prime (718138931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 359069460 + 359069461.

It is an arithmetic number, because the mean of its divisors is an integer number (359069461).

Almost surely, 2^718138921 is an apocalyptic number.

It is an amenable number.

718138921 is a deficient number, since it is larger than the sum of its proper divisors (1).

718138921 is an equidigital number, since it uses as much as digits as its factorization.

718138921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24192, while the sum is 40.

The square root of 718138921 is about 26798.1141314086. The cubic root of 718138921 is about 895.5080377699.

The spelling of 718138921 in words is "seven hundred eighteen million, one hundred thirty-eight thousand, nine hundred twenty-one".