51381851021 has 2 divisors, whose sum is σ = 51381851022. Its totient is φ = 51381851020.

The previous prime is 51381850997. The next prime is 51381851173. The reversal of 51381851021 is 12015818315.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50917922500 + 463928521 = 225650^2 + 21539^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51381851021 is a prime.

It is a super-2 number, since 2×51381851021² (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 (51381851921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25690925510 + 25690925511.

It is an arithmetic number, because the mean of its divisors is an integer number (25690925511).

Almost surely, 2^51381851021 is an apocalyptic number.

It is an amenable number.

51381851021 is a deficient number, since it is larger than the sum of its proper divisors (1).

51381851021 is an equidigital number, since it uses as much as digits as its factorization.

51381851021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9600, while the sum is 35.

The spelling of 51381851021 in words is "fifty-one billion, three hundred eighty-one million, eight hundred fifty-one thousand, twenty-one".