721316161 has 4 divisors (see below), whose sum is σ = 724059072. Its totient is φ = 718573252.

The previous prime is 721316149. The next prime is 721316173. The reversal of 721316161 is 161613127.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (721316149) and next prime (721316173).

It is a cyclic number.

It is not a de Polignac number, because 721316161 - 2⁵ = 721316129 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721316131) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1371061 + ... + 1371586.

It is an arithmetic number, because the mean of its divisors is an integer number (181014768).

Almost surely, 2^721316161 is an apocalyptic number.

It is an amenable number.

721316161 is a deficient number, since it is larger than the sum of its proper divisors (2742911).

721316161 is a wasteful number, since it uses less digits than its factorization.

721316161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2742910.

The product of its digits is 1512, while the sum is 28.

The square root of 721316161 is about 26857.3297444106. The cubic root of 721316161 is about 896.8267511443.

Adding to 721316161 its reverse (161613127), we get a palindrome (882929288).

The spelling of 721316161 in words is "seven hundred twenty-one million, three hundred sixteen thousand, one hundred sixty-one".