828920721 has 4 divisors (see below), whose sum is σ = 1105227632. Its totient is φ = 552613812.

The previous prime is 828920711. The next prime is 828920783. The reversal of 828920721 is 127029828.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 828920721 - 2¹⁵ = 828887953 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 828920721.

It is not an unprimeable number, because it can be changed into a prime (828920711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 138153451 + ... + 138153456.

It is an arithmetic number, because the mean of its divisors is an integer number (276306908).

Almost surely, 2^828920721 is an apocalyptic number.

It is an amenable number.

828920721 is a deficient number, since it is larger than the sum of its proper divisors (276306911).

828920721 is a wasteful number, since it uses less digits than its factorization.

828920721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 276306910.

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 828920721 is about 28790.9833281185. The cubic root of 828920721 is about 939.3721176631.

The spelling of 828920721 in words is "eight hundred twenty-eight million, nine hundred twenty thousand, seven hundred twenty-one".