721580161 has 2 divisors, whose sum is σ = 721580162. Its totient is φ = 721580160.

The previous prime is 721580137. The next prime is 721580177. The reversal of 721580161 is 161085127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 384160000 + 337420161 = 19600^2 + 18369^2 .

It is a cyclic number.

It is not a de Polignac number, because 721580161 - 2⁵ = 721580129 is a prime.

It is not a weakly prime, because it can be changed into another prime (721580131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360790080 + 360790081.

It is an arithmetic number, because the mean of its divisors is an integer number (360790081).

Almost surely, 2^721580161 is an apocalyptic number.

It is an amenable number.

721580161 is a deficient number, since it is larger than the sum of its proper divisors (1).

721580161 is an equidigital number, since it uses as much as digits as its factorization.

721580161 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3360, while the sum is 31.

The square root of 721580161 is about 26862.2441542028. The cubic root of 721580161 is about 896.9361499517.

The spelling of 721580161 in words is "seven hundred twenty-one million, five hundred eighty thousand, one hundred sixty-one".