721691441 has 2 divisors, whose sum is σ = 721691442. Its totient is φ = 721691440.

The previous prime is 721691423. The next prime is 721691449. The reversal of 721691441 is 144196127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 695640625 + 26050816 = 26375^2 + 5104^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721691441 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (721691449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360845720 + 360845721.

It is an arithmetic number, because the mean of its divisors is an integer number (360845721).

Almost surely, 2^721691441 is an apocalyptic number.

It is an amenable number.

721691441 is a deficient number, since it is larger than the sum of its proper divisors (1).

721691441 is an equidigital number, since it uses as much as digits as its factorization.

721691441 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12096, while the sum is 35.

The square root of 721691441 is about 26864.3153830504. The cubic root of 721691441 is about 896.9822552124.

The spelling of 721691441 in words is "seven hundred twenty-one million, six hundred ninety-one thousand, four hundred forty-one".