721307663 has 4 divisors (see below), whose sum is σ = 722020728. Its totient is φ = 720594600.

The previous prime is 721307647. The next prime is 721307681. The reversal of 721307663 is 366703127.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 721307663 - 2⁴ = 721307647 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721303663) 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, 355013 + ... + 357038.

It is an arithmetic number, because the mean of its divisors is an integer number (180505182).

Almost surely, 2^721307663 is an apocalyptic number.

721307663 is a deficient number, since it is larger than the sum of its proper divisors (713065).

721307663 is a wasteful number, since it uses less digits than its factorization.

721307663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 713064.

The product of its (nonzero) digits is 31752, while the sum is 35.

The square root of 721307663 is about 26857.1715375987. The cubic root of 721307663 is about 896.8232292196.

The spelling of 721307663 in words is "seven hundred twenty-one million, three hundred seven thousand, six hundred sixty-three".