51556640210221 has 2 divisors, whose sum is σ = 51556640210222. Its totient is φ = 51556640210220.

The previous prime is 51556640210147. The next prime is 51556640210249. The reversal of 51556640210221 is 12201204665515.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 51300618378025 + 256021832196 = 7162445^2 + 505986^2 .

It is a cyclic number.

It is not a de Polignac number, because 51556640210221 - 2⁷ = 51556640210093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51556640210261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25778320105110 + 25778320105111.

It is an arithmetic number, because the mean of its divisors is an integer number (25778320105111).

Almost surely, 2^{51556640210221} is an apocalyptic number.

It is an amenable number.

51556640210221 is a deficient number, since it is larger than the sum of its proper divisors (1).

51556640210221 is an equidigital number, since it uses as much as digits as its factorization.

51556640210221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144000, while the sum is 40.

Adding to 51556640210221 its reverse (12201204665515), we get a palindrome (63757844875736).

The spelling of 51556640210221 in words is "fifty-one trillion, five hundred fifty-six billion, six hundred forty million, two hundred ten thousand, two hundred twenty-one".