721991603 has 2 divisors, whose sum is σ = 721991604. Its totient is φ = 721991602.

The previous prime is 721991593. The next prime is 721991609. The reversal of 721991603 is 306199127.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 721991603 - 2⁴ = 721991587 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (721991609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360995801 + 360995802.

It is an arithmetic number, because the mean of its divisors is an integer number (360995802).

Almost surely, 2^721991603 is an apocalyptic number.

721991603 is a deficient number, since it is larger than the sum of its proper divisors (1).

721991603 is an equidigital number, since it uses as much as digits as its factorization.

721991603 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20412, while the sum is 38.

The square root of 721991603 is about 26869.9014326439. The cubic root of 721991603 is about 897.1065939783.

The spelling of 721991603 in words is "seven hundred twenty-one million, nine hundred ninety-one thousand, six hundred three".