51216779521 has 2 divisors, whose sum is σ = 51216779522. Its totient is φ = 51216779520.

The previous prime is 51216779519. The next prime is 51216779533. The reversal of 51216779521 is 12597761215.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50823193600 + 393585921 = 225440^2 + 19839^2 .

It is a cyclic number.

It is not a de Polignac number, because 51216779521 - 2¹ = 51216779519 is a prime.

Together with 51216779519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (51216779501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25608389760 + 25608389761.

It is an arithmetic number, because the mean of its divisors is an integer number (25608389761).

Almost surely, 2^51216779521 is an apocalyptic number.

It is an amenable number.

51216779521 is a deficient number, since it is larger than the sum of its proper divisors (1).

51216779521 is an equidigital number, since it uses as much as digits as its factorization.

51216779521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 264600, while the sum is 46.

The spelling of 51216779521 in words is "fifty-one billion, two hundred sixteen million, seven hundred seventy-nine thousand, five hundred twenty-one".