81638655 has 48 divisors (see below), whose sum is σ = 156893184. Its totient is φ = 36106560.

The previous prime is 81638653. The next prime is 81638659. The reversal of 81638655 is 55683618.

It is not a de Polignac number, because 81638655 - 2¹ = 81638653 is a prime.

It is a super-3 number, since 3×81638655³ (a number of 25 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81638651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 20994 + ... + 24576.

It is an arithmetic number, because the mean of its divisors is an integer number (3268608).

Almost surely, 2^81638655 is an apocalyptic number.

81638655 is a deficient number, since it is larger than the sum of its proper divisors (75254529).

81638655 is a wasteful number, since it uses less digits than its factorization.

81638655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3636 (or 3629 counting only the distinct ones).

The product of its digits is 172800, while the sum is 42.

The square root of 81638655 is about 9035.4111693935. The cubic root of 81638655 is about 433.8090557888.

The spelling of 81638655 in words is "eighty-one million, six hundred thirty-eight thousand, six hundred fifty-five".