721691423 has 2 divisors, whose sum is σ = 721691424. Its totient is φ = 721691422.

The previous prime is 721691387. The next prime is 721691441. The reversal of 721691423 is 324196127.

It is a strong prime.

It is an emirp because it is prime and its reverse (324196127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 721691423 - 2²⁰ = 720642847 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721691473) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360845711 + 360845712.

It is an arithmetic number, because the mean of its divisors is an integer number (360845712).

Almost surely, 2^721691423 is an apocalyptic number.

721691423 is a deficient number, since it is larger than the sum of its proper divisors (1).

721691423 is an equidigital number, since it uses as much as digits as its factorization.

721691423 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 35.

The square root of 721691423 is about 26864.3150480335. The cubic root of 721691423 is about 896.9822477551.

The spelling of 721691423 in words is "seven hundred twenty-one million, six hundred ninety-one thousand, four hundred twenty-three".