81357389 has 2 divisors, whose sum is σ = 81357390. Its totient is φ = 81357388.

The previous prime is 81357379. The next prime is 81357391. The reversal of 81357389 is 98375318.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80820100 + 537289 = 8990^2 + 733^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81357389 is a prime.

Together with 81357391, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81357319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40678694 + 40678695.

It is an arithmetic number, because the mean of its divisors is an integer number (40678695).

Almost surely, 2^81357389 is an apocalyptic number.

It is an amenable number.

81357389 is a deficient number, since it is larger than the sum of its proper divisors (1).

81357389 is an equidigital number, since it uses as much as digits as its factorization.

81357389 is an evil number, because the sum of its binary digits is even.

The product of its digits is 181440, while the sum is 44.

The square root of 81357389 is about 9019.8330915821. The cubic root of 81357389 is about 433.3102882551.

The spelling of 81357389 in words is "eighty-one million, three hundred fifty-seven thousand, three hundred eighty-nine".