81438613 has 2 divisors, whose sum is σ = 81438614. Its totient is φ = 81438612.

The previous prime is 81438611. The next prime is 81438629. The reversal of 81438613 is 31683418.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65254084 + 16184529 = 8078^2 + 4023^2 .

It is a cyclic number.

It is not a de Polignac number, because 81438613 - 2¹ = 81438611 is a prime.

Together with 81438611, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81438611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40719306 + 40719307.

It is an arithmetic number, because the mean of its divisors is an integer number (40719307).

Almost surely, 2^81438613 is an apocalyptic number.

It is an amenable number.

81438613 is a deficient number, since it is larger than the sum of its proper divisors (1).

81438613 is an equidigital number, since it uses as much as digits as its factorization.

81438613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13824, while the sum is 34.

The square root of 81438613 is about 9024.3344906979. The cubic root of 81438613 is about 433.4544402462.

The spelling of 81438613 in words is "eighty-one million, four hundred thirty-eight thousand, six hundred thirteen".