51561110240221 has 4 divisors (see below), whose sum is σ = 51570888570972. Its totient is φ = 51551331909472.

The previous prime is 51561110240219. The next prime is 51561110240249. The reversal of 51561110240221 is 12204201116515.

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 32751012122500 + 18810098117721 = 5722850^2 + 4337061^2 .

It is a cyclic number.

It is not a de Polignac number, because 51561110240221 - 2¹ = 51561110240219 is a prime.

It is a super-2 number, since 2×51561110240221² (a number of 28 digits) 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 (51561110243221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4889157466 + ... + 4889168011.

It is an arithmetic number, because the mean of its divisors is an integer number (12892722142743).

Almost surely, 2^{51561110240221} is an apocalyptic number.

It is an amenable number.

51561110240221 is a deficient number, since it is larger than the sum of its proper divisors (9778330751).

51561110240221 is an equidigital number, since it uses as much as digits as its factorization.

51561110240221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9778330750.

The product of its (nonzero) digits is 4800, while the sum is 31.

Adding to 51561110240221 its reverse (12204201116515), we get a palindrome (63765311356736).

The spelling of 51561110240221 in words is "fifty-one trillion, five hundred sixty-one billion, one hundred ten million, two hundred forty thousand, two hundred twenty-one".