820003721 has 4 divisors (see below), whose sum is σ = 868239252. Its totient is φ = 771768192.

The previous prime is 820003711. The next prime is 820003741. The reversal of 820003721 is 127300028.

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 310147321 + 509856400 = 17611^2 + 22580^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-820003721 is a prime.

It is a super-2 number, since 2×820003721² = 1344812204907691682, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (820003711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24117740 + ... + 24117773.

It is an arithmetic number, because the mean of its divisors is an integer number (217059813).

Almost surely, 2^820003721 is an apocalyptic number.

It is an amenable number.

820003721 is a deficient number, since it is larger than the sum of its proper divisors (48235531).

820003721 is a wasteful number, since it uses less digits than its factorization.

820003721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48235530.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 820003721 is about 28635.7070979573. The cubic root of 820003721 is about 935.9915780922.

Adding to 820003721 its reverse (127300028), we get a palindrome (947303749).

The spelling of 820003721 in words is "eight hundred twenty million, three thousand, seven hundred twenty-one".