81638667 has 24 divisors (see below), whose sum is σ = 131786928. Its totient is φ = 48268800.

The previous prime is 81638659. The next prime is 81638681. The reversal of 81638667 is 76683618.

81638667 is a `hidden beast` number, since 8 + 1 + 638 + 6 + 6 + 7 = 666.

It is not a de Polignac number, because 81638667 - 2³ = 81638659 is a prime.

It is a super-3 number, since 3×81638667³ (a number of 25 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (81638647) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5998 + ... + 14115.

It is an arithmetic number, because the mean of its divisors is an integer number (5491122).

Almost surely, 2^81638667 is an apocalyptic number.

81638667 is a deficient number, since it is larger than the sum of its proper divisors (50148261).

81638667 is a wasteful number, since it uses less digits than its factorization.

81638667 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20171 (or 20168 counting only the distinct ones).

The product of its digits is 290304, while the sum is 45.

The square root of 81638667 is about 9035.4118334473. The cubic root of 81638667 is about 433.8090770438.

The spelling of 81638667 in words is "eighty-one million, six hundred thirty-eight thousand, six hundred sixty-seven".