81728653 has 2 divisors, whose sum is σ = 81728654. Its totient is φ = 81728652.

The previous prime is 81728609. The next prime is 81728657. The reversal of 81728653 is 35682718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72131049 + 9597604 = 8493^2 + 3098^2 .

It is a cyclic number.

It is not a de Polignac number, because 81728653 - 2²¹ = 79631501 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81728657) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40864326 + 40864327.

It is an arithmetic number, because the mean of its divisors is an integer number (40864327).

Almost surely, 2^81728653 is an apocalyptic number.

It is an amenable number.

81728653 is a deficient number, since it is larger than the sum of its proper divisors (1).

81728653 is an equidigital number, since it uses as much as digits as its factorization.

81728653 is an evil number, because the sum of its binary digits is even.

The product of its digits is 80640, while the sum is 40.

The square root of 81728653 is about 9040.3900911410. The cubic root of 81728653 is about 433.9684068120.

The spelling of 81728653 in words is "eighty-one million, seven hundred twenty-eight thousand, six hundred fifty-three".