816445721 has 32 divisors (see below), whose sum is σ = 1022036736. Its totient is φ = 635040000.

The previous prime is 816445711. The next prime is 816445727. The reversal of 816445721 is 127544618.

816445721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 816445721 - 2⁶ = 816445657 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (816445727) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1939091 + ... + 1939511.

It is an arithmetic number, because the mean of its divisors is an integer number (31938648).

Almost surely, 2^816445721 is an apocalyptic number.

It is an amenable number.

816445721 is a deficient number, since it is larger than the sum of its proper divisors (205591015).

816445721 is a wasteful number, since it uses less digits than its factorization.

816445721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 753.

The product of its digits is 53760, while the sum is 38.

The square root of 816445721 is about 28573.5143270827. The cubic root of 816445721 is about 934.6358580866.

The spelling of 816445721 in words is "eight hundred sixteen million, four hundred forty-five thousand, seven hundred twenty-one".