721101391 has 2 divisors, whose sum is σ = 721101392. Its totient is φ = 721101390.

The previous prime is 721101389. The next prime is 721101413. The reversal of 721101391 is 193101127.

It is a weak prime.

It is an emirp because it is prime and its reverse (193101127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 721101391 - 2¹ = 721101389 is a prime.

It is a super-2 number, since 2×721101391² = 1039974432204269762, which contains 22 as substring.

Together with 721101389, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721107391) 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, 360550695 + 360550696.

It is an arithmetic number, because the mean of its divisors is an integer number (360550696).

Almost surely, 2^721101391 is an apocalyptic number.

721101391 is a deficient number, since it is larger than the sum of its proper divisors (1).

721101391 is an equidigital number, since it uses as much as digits as its factorization.

721101391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 378, while the sum is 25.

The square root of 721101391 is about 26853.3310969049. The cubic root of 721101391 is about 896.7377330357.

The spelling of 721101391 in words is "seven hundred twenty-one million, one hundred one thousand, three hundred ninety-one".