81355381 has 2 divisors, whose sum is σ = 81355382. Its totient is φ = 81355380.

The previous prime is 81355363. The next prime is 81355453. The reversal of 81355381 is 18355318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 79299025 + 2056356 = 8905^2 + 1434^2 .

It is a cyclic number.

It is not a de Polignac number, because 81355381 - 2⁵ = 81355349 is a prime.

It is a super-2 number, since 2×81355381² = 13237396035310322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81355331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40677690 + 40677691.

It is an arithmetic number, because the mean of its divisors is an integer number (40677691).

Almost surely, 2^81355381 is an apocalyptic number.

It is an amenable number.

81355381 is a deficient number, since it is larger than the sum of its proper divisors (1).

81355381 is an equidigital number, since it uses as much as digits as its factorization.

81355381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14400, while the sum is 34.

The square root of 81355381 is about 9019.7217806316. The cubic root of 81355381 is about 433.3067233495.

The spelling of 81355381 in words is "eighty-one million, three hundred fifty-five thousand, three hundred eighty-one".