721943161 has 9 divisors (see below), whose sum is σ = 732105549. Its totient is φ = 711921024.

The previous prime is 721943147. The next prime is 721943177. The reversal of 721943161 is 161349127.

The square root of 721943161 is 26869.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 113827561 + 608115600 = 10669^2 + 24660^2 .

It is not a de Polignac number, because 721943161 - 2²⁹ = 185072249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721943111) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2606155 + ... + 2606431.

It is an arithmetic number, because the mean of its divisors is an integer number (81345061).

Almost surely, 2^721943161 is an apocalyptic number.

721943161 is the 26869-th square number.

721943161 is the 13435-th centered octagonal number.

It is an amenable number.

721943161 is a deficient number, since it is larger than the sum of its proper divisors (10162388).

721943161 is an frugal number, since it uses more digits than its factorization.

721943161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 748 (or 374 counting only the distinct ones).

The product of its digits is 9072, while the sum is 34.

The cubic root of 721943161 is about 897.0865297516.

The spelling of 721943161 in words is "seven hundred twenty-one million, nine hundred forty-three thousand, one hundred sixty-one".