51981613 has 2 divisors, whose sum is σ = 51981614. Its totient is φ = 51981612.

The previous prime is 51981583. The next prime is 51981647. The reversal of 51981613 is 31618915.

51981613 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an a-pointer prime, because the next prime (51981647) can be obtained adding 51981613 to its sum of digits (34).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 49603849 + 2377764 = 7043^2 + 1542^2 .

It is a cyclic number.

It is not a de Polignac number, because 51981613 - 2⁵ = 51981581 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51981313) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25990806 + 25990807.

It is an arithmetic number, because the mean of its divisors is an integer number (25990807).

Almost surely, 2^51981613 is an apocalyptic number.

It is an amenable number.

51981613 is a deficient number, since it is larger than the sum of its proper divisors (1).

51981613 is an equidigital number, since it uses as much as digits as its factorization.

51981613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6480, while the sum is 34.

The square root of 51981613 is about 7209.8275291438. The cubic root of 51981613 is about 373.2071171091.

The spelling of 51981613 in words is "fifty-one million, nine hundred eighty-one thousand, six hundred thirteen".