720991 has 2 divisors, whose sum is σ = 720992. Its totient is φ = 720990.

The previous prime is 720983. The next prime is 720997. The reversal of 720991 is 199027.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 720991 - 2³ = 720983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (720997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360495 + 360496.

It is an arithmetic number, because the mean of its divisors is an integer number (360496).

2⁷²⁰⁹⁹¹ is an apocalyptic number.

720991 is a deficient number, since it is larger than the sum of its proper divisors (1).

720991 is an equidigital number, since it uses as much as digits as its factorization.

720991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1134, while the sum is 28.

The square root of 720991 is about 849.1118889758. Note that the first 3 decimals coincide. The cubic root of 720991 is about 89.6691971174.

It can be divided in two parts, 720 and 991, that added together give a triangular number (1711 = T₅₈).

The spelling of 720991 in words is "seven hundred twenty thousand, nine hundred ninety-one".