81897493 has 4 divisors (see below), whose sum is σ = 81922860. Its totient is φ = 81872128.

The previous prime is 81897481. The next prime is 81897509. The reversal of 81897493 is 39479818.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1580049 + 80317444 = 1257^2 + 8962^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81897493 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81897793) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6988 + ... + 14581.

It is an arithmetic number, because the mean of its divisors is an integer number (20480715).

Almost surely, 2^81897493 is an apocalyptic number.

It is an amenable number.

81897493 is a deficient number, since it is larger than the sum of its proper divisors (25367).

81897493 is a wasteful number, since it uses less digits than its factorization.

81897493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25366.

The product of its digits is 435456, while the sum is 49.

The square root of 81897493 is about 9049.7233659378. The cubic root of 81897493 is about 434.2670406648.

The spelling of 81897493 in words is "eighty-one million, eight hundred ninety-seven thousand, four hundred ninety-three".