721555097 has 4 divisors (see below), whose sum is σ = 723221940. Its totient is φ = 719888256.

The previous prime is 721555069. The next prime is 721555151. The reversal of 721555097 is 790555127.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 50537881 + 671017216 = 7109^2 + 25904^2 .

It is a cyclic number.

It is not a de Polignac number, because 721555097 - 2⁶ = 721555033 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721555027) 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, 832772 + ... + 833637.

It is an arithmetic number, because the mean of its divisors is an integer number (180805485).

Almost surely, 2^721555097 is an apocalyptic number.

It is an amenable number.

721555097 is a deficient number, since it is larger than the sum of its proper divisors (1666843).

721555097 is a wasteful number, since it uses less digits than its factorization.

721555097 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1666842.

The product of its (nonzero) digits is 110250, while the sum is 41.

The square root of 721555097 is about 26861.7776217435. Note that the first 3 decimals coincide. The cubic root of 721555097 is about 896.9257648418.

The spelling of 721555097 in words is "seven hundred twenty-one million, five hundred fifty-five thousand, ninety-seven".