721391189 has 2 divisors, whose sum is σ = 721391190. Its totient is φ = 721391188.

The previous prime is 721391179. The next prime is 721391197. The reversal of 721391189 is 981193127.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 637815025 + 83576164 = 25255^2 + 9142^2 .

It is an emirp because it is prime and its reverse (981193127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 721391189 - 2¹⁶ = 721325653 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721391149) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360695594 + 360695595.

It is an arithmetic number, because the mean of its divisors is an integer number (360695595).

Almost surely, 2^721391189 is an apocalyptic number.

It is an amenable number.

721391189 is a deficient number, since it is larger than the sum of its proper divisors (1).

721391189 is an equidigital number, since it uses as much as digits as its factorization.

721391189 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27216, while the sum is 41.

The square root of 721391189 is about 26858.7264962433. The cubic root of 721391189 is about 896.8578446686.

The spelling of 721391189 in words is "seven hundred twenty-one million, three hundred ninety-one thousand, one hundred eighty-nine".