721677391 has 2 divisors, whose sum is σ = 721677392. Its totient is φ = 721677390.

The previous prime is 721677379. The next prime is 721677401. The reversal of 721677391 is 193776127.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 721677391 - 2⁷ = 721677263 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721677311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360838695 + 360838696.

It is an arithmetic number, because the mean of its divisors is an integer number (360838696).

Almost surely, 2^721677391 is an apocalyptic number.

721677391 is a deficient number, since it is larger than the sum of its proper divisors (1).

721677391 is an equidigital number, since it uses as much as digits as its factorization.

721677391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 111132, while the sum is 43.

The square root of 721677391 is about 26864.0538824653. The cubic root of 721677391 is about 896.9764343118.

The spelling of 721677391 in words is "seven hundred twenty-one million, six hundred seventy-seven thousand, three hundred ninety-one".