821059721 has 4 divisors (see below), whose sum is σ = 821169732. Its totient is φ = 820949712.

The previous prime is 821059669. The next prime is 821059739. The reversal of 821059721 is 127950128.

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 753228025 + 67831696 = 27445^2 + 8236^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-821059721 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (821059751) 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, 42926 + ... + 59031.

It is an arithmetic number, because the mean of its divisors is an integer number (205292433).

Almost surely, 2^821059721 is an apocalyptic number.

It is an amenable number.

821059721 is a deficient number, since it is larger than the sum of its proper divisors (110011).

821059721 is a wasteful number, since it uses less digits than its factorization.

821059721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110010.

The product of its (nonzero) digits is 10080, while the sum is 35.

The square root of 821059721 is about 28654.1396834733. The cubic root of 821059721 is about 936.3931954242.

The spelling of 821059721 in words is "eight hundred twenty-one million, fifty-nine thousand, seven hundred twenty-one".