721616501 has 2 divisors, whose sum is σ = 721616502. Its totient is φ = 721616500.

The previous prime is 721616491. The next prime is 721616537. The reversal of 721616501 is 105616127.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 443060401 + 278556100 = 21049^2 + 16690^2 .

It is a cyclic number.

It is not a de Polignac number, because 721616501 - 2⁶ = 721616437 is a prime.

It is a Chen prime.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721616591) 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, 360808250 + 360808251.

It is an arithmetic number, because the mean of its divisors is an integer number (360808251).

Almost surely, 2^721616501 is an apocalyptic number.

It is an amenable number.

721616501 is a deficient number, since it is larger than the sum of its proper divisors (1).

721616501 is an equidigital number, since it uses as much as digits as its factorization.

721616501 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 721616501 is about 26862.9205597604. The cubic root of 721616501 is about 896.9512067739.

The spelling of 721616501 in words is "seven hundred twenty-one million, six hundred sixteen thousand, five hundred one".