819945721 has 8 divisors (see below), whose sum is σ = 941174720. Its totient is φ = 699740208.

The previous prime is 819945677. The next prime is 819945727. The reversal of 819945721 is 127549918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 819945721 - 2¹³ = 819937529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (819945727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 254151 + ... + 257356.

It is an arithmetic number, because the mean of its divisors is an integer number (117646840).

Almost surely, 2^819945721 is an apocalyptic number.

It is an amenable number.

819945721 is a deficient number, since it is larger than the sum of its proper divisors (121228999).

819945721 is a wasteful number, since it uses less digits than its factorization.

819945721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 511743.

The product of its digits is 181440, while the sum is 46.

The square root of 819945721 is about 28634.6943584177. The cubic root of 819945721 is about 935.9695095779.

The spelling of 819945721 in words is "eight hundred nineteen million, nine hundred forty-five thousand, seven hundred twenty-one".