51761221981 has 12 divisors (see below), whose sum is σ = 60446336508. Its totient is φ = 44194117632.

The previous prime is 51761221931. The next prime is 51761222027. The reversal of 51761221981 is 18912216715.

It can be written as a sum of positive squares in 2 ways, for example, as 43528563225 + 8232658756 = 208635^2 + 90734^2 .

It is not a de Polignac number, because 51761221981 - 2⁹ = 51761221469 is a prime.

It is a super-2 number, since 2×51761221981² (a number of 22 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 (51761221931) 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 11 ways as a sum of consecutive naturals, for example, 2042566 + ... + 2067751.

It is an arithmetic number, because the mean of its divisors is an integer number (5037194709).

Almost surely, 2^51761221981 is an apocalyptic number.

It is an amenable number.

51761221981 is a deficient number, since it is larger than the sum of its proper divisors (8685114527).

51761221981 is a wasteful number, since it uses less digits than its factorization.

51761221981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4110588 (or 4110581 counting only the distinct ones).

The product of its digits is 60480, while the sum is 43.

The spelling of 51761221981 in words is "fifty-one billion, seven hundred sixty-one million, two hundred twenty-one thousand, nine hundred eighty-one".