51681988261 has 2 divisors, whose sum is σ = 51681988262. Its totient is φ = 51681988260.

The previous prime is 51681988219. The next prime is 51681988289. The reversal of 51681988261 is 16288918615.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 41595602500 + 10086385761 = 203950^2 + 100431^2 .

It is a cyclic number.

It is not a de Polignac number, because 51681988261 - 2¹³ = 51681980069 is a prime.

It is a super-2 number, since 2×51681988261² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51681980261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25840994130 + 25840994131.

It is an arithmetic number, because the mean of its divisors is an integer number (25840994131).

Almost surely, 2^51681988261 is an apocalyptic number.

It is an amenable number.

51681988261 is a deficient number, since it is larger than the sum of its proper divisors (1).

51681988261 is an equidigital number, since it uses as much as digits as its factorization.

51681988261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1658880, while the sum is 55.

The spelling of 51681988261 in words is "fifty-one billion, six hundred eighty-one million, nine hundred eighty-eight thousand, two hundred sixty-one".