81355493 has 2 divisors, whose sum is σ = 81355494. Its totient is φ = 81355492.

The previous prime is 81355471. The next prime is 81355541. The reversal of 81355493 is 39455318.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64529089 + 16826404 = 8033^2 + 4102^2 .

It is a cyclic number.

It is not a de Polignac number, because 81355493 - 2²⁰ = 80306917 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81355453) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40677746 + 40677747.

It is an arithmetic number, because the mean of its divisors is an integer number (40677747).

Almost surely, 2^81355493 is an apocalyptic number.

It is an amenable number.

81355493 is a deficient number, since it is larger than the sum of its proper divisors (1).

81355493 is an equidigital number, since it uses as much as digits as its factorization.

81355493 is an evil number, because the sum of its binary digits is even.

The product of its digits is 64800, while the sum is 38.

The square root of 81355493 is about 9019.7279892467. The cubic root of 81355493 is about 433.3069221904.

The spelling of 81355493 in words is "eighty-one million, three hundred fifty-five thousand, four hundred ninety-three".