721506385 has 4 divisors (see below), whose sum is σ = 865807668. Its totient is φ = 577205104.

The previous prime is 721506371. The next prime is 721506419. The reversal of 721506385 is 583605127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 583605127 = 7 ⋅83372161.

It can be written as a sum of positive squares in 2 ways, for example, as 271557441 + 449948944 = 16479^2 + 21212^2 .

It is a cyclic number.

It is not a de Polignac number, because 721506385 - 2⁷ = 721506257 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 72150634 + ... + 72150643.

It is an arithmetic number, because the mean of its divisors is an integer number (216451917).

Almost surely, 2^721506385 is an apocalyptic number.

It is an amenable number.

721506385 is a deficient number, since it is larger than the sum of its proper divisors (144301283).

721506385 is a wasteful number, since it uses less digits than its factorization.

721506385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144301282.

The product of its (nonzero) digits is 50400, while the sum is 37.

The square root of 721506385 is about 26860.8708905724. The cubic root of 721506385 is about 896.9055806446.

The spelling of 721506385 in words is "seven hundred twenty-one million, five hundred six thousand, three hundred eighty-five".