561802020821 has 8 divisors (see below), whose sum is σ = 562106464920. Its totient is φ = 561497655808.

The previous prime is 561802020803. The next prime is 561802020839. The reversal of 561802020821 is 128020208165.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (561802020803) and next prime (561802020839).

It can be written as a sum of positive squares in 4 ways, for example, as 150005163025 + 411796857796 = 387305^2 + 641714^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 561802020821 - 2²⁶ = 561734911957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (561802020421) 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, 18693635 + ... + 18723663.

It is an arithmetic number, because the mean of its divisors is an integer number (70263308115).

Almost surely, 2^561802020821 is an apocalyptic number.

It is an amenable number.

561802020821 is a deficient number, since it is larger than the sum of its proper divisors (304444099).

561802020821 is a wasteful number, since it uses less digits than its factorization.

561802020821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39543.

The product of its (nonzero) digits is 15360, while the sum is 35.

Adding to 561802020821 its reverse (128020208165), we get a palindrome (689822228986).

The spelling of 561802020821 in words is "five hundred sixty-one billion, eight hundred two million, twenty thousand, eight hundred twenty-one".