8021561 has 4 divisors (see below), whose sum is σ = 8153124. Its totient is φ = 7890000.

The previous prime is 8021539. The next prime is 8021567. The reversal of 8021561 is 1651208.

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 3097600 + 4923961 = 1760^2 + 2219^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8021561 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 (8021567) 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, 65690 + ... + 65811.

It is an arithmetic number, because the mean of its divisors is an integer number (2038281).

Almost surely, 2^8021561 is an apocalyptic number.

It is an amenable number.

8021561 is a deficient number, since it is larger than the sum of its proper divisors (131563).

8021561 is a wasteful number, since it uses less digits than its factorization.

8021561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131562.

The product of its (nonzero) digits is 480, while the sum is 23.

The square root of 8021561 is about 2832.2360424230. The cubic root of 8021561 is about 200.1795138257.

Adding to 8021561 its reverse (1651208), we get a palindrome (9672769).

The spelling of 8021561 in words is "eight million, twenty-one thousand, five hundred sixty-one".