721139 has 2 divisors, whose sum is σ = 721140. Its totient is φ = 721138.

The previous prime is 721129. The next prime is 721141. The reversal of 721139 is 931127.

It is a strong prime.

It is an emirp because it is prime and its reverse (931127) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721139 is a prime.

It is a Sophie Germain prime.

Together with 721141, it forms a pair of twin primes.

It is a Chen prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721139.

It is not a weakly prime, because it can be changed into another prime (721109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360569 + 360570.

It is an arithmetic number, because the mean of its divisors is an integer number (360570).

2⁷²¹¹³⁹ is an apocalyptic number.

721139 is a deficient number, since it is larger than the sum of its proper divisors (1).

721139 is an equidigital number, since it uses as much as digits as its factorization.

721139 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 378, while the sum is 23.

The square root of 721139 is about 849.1990343848. The cubic root of 721139 is about 89.6753322532.

The spelling of 721139 in words is "seven hundred twenty-one thousand, one hundred thirty-nine".