81663471 has 20 divisors (see below), whose sum is σ = 122542992. Its totient is φ = 54196128.

The previous prime is 81663443. The next prime is 81663479. The reversal of 81663471 is 17436618.

81663471 is a `hidden beast` number, since 8 + 16 + 634 + 7 + 1 = 666.

It is not a de Polignac number, because 81663471 - 2⁷ = 81663343 is a prime.

It is a super-3 number, since 3×81663471³ (a number of 25 digits) contains 333 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81663479) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 16710 + ... + 21036.

Almost surely, 2^81663471 is an apocalyptic number.

81663471 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

81663471 is a deficient number, since it is larger than the sum of its proper divisors (40879521).

81663471 is a wasteful number, since it uses less digits than its factorization.

81663471 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4572 (or 4563 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 81663471 is about 9036.7843285098. The cubic root of 81663471 is about 433.8530068432.

The spelling of 81663471 in words is "eighty-one million, six hundred sixty-three thousand, four hundred seventy-one".