81955665 has 64 divisors (see below), whose sum is σ = 160300800. Its totient is φ = 39398400.

The previous prime is 81955663. The next prime is 81955697. The reversal of 81955665 is 56655918.

It is a happy number.

81955665 is a `hidden beast` number, since 81 + 9 + 5 + 566 + 5 = 666.

It is not a de Polignac number, because 81955665 - 2¹ = 81955663 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 81955665.

It is not an unprimeable number, because it can be changed into a prime (81955663) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 339945 + ... + 340185.

It is an arithmetic number, because the mean of its divisors is an integer number (2504700).

Almost surely, 2^81955665 is an apocalyptic number.

It is an amenable number.

81955665 is a deficient number, since it is larger than the sum of its proper divisors (78345135).

81955665 is a wasteful number, since it uses less digits than its factorization.

81955665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 495 (or 489 counting only the distinct ones).

The product of its digits is 324000, while the sum is 45.

The square root of 81955665 is about 9052.9368163044. The cubic root of 81955665 is about 434.3698366621.

The spelling of 81955665 in words is "eighty-one million, nine hundred fifty-five thousand, six hundred sixty-five".