1028921821 has 8 divisors (see below), whose sum is σ = 1089734904. Its totient is φ = 968140800.

The previous prime is 1028921809. The next prime is 1028921843. The reversal of 1028921821 is 1281298201.

It can be written as a sum of positive squares in 4 ways, for example, as 589809796 + 439112025 = 24286^2 + 20955^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1028921821 is a prime.

It is a super-2 number, since 2×1028921821² = 2117360227459912082, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1028921891) 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, 98971 + ... + 108871.

It is an arithmetic number, because the mean of its divisors is an integer number (136216863).

Almost surely, 2^1028921821 is an apocalyptic number.

It is an amenable number.

1028921821 is a deficient number, since it is larger than the sum of its proper divisors (60813083).

1028921821 is an equidigital number, since it uses as much as digits as its factorization.

1028921821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16031.

The product of its (nonzero) digits is 4608, while the sum is 34.

The square root of 1028921821 is about 32076.8112660844. The cubic root of 1028921821 is about 1009.5491308513.

The spelling of 1028921821 in words is "one billion, twenty-eight million, nine hundred twenty-one thousand, eight hundred twenty-one".