81655811 has 4 divisors (see below), whose sum is σ = 86459112. Its totient is φ = 76852512.

The previous prime is 81655807. The next prime is 81655813. The reversal of 81655811 is 11855618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 11855618 = 2 ⋅5927809.

It is not a de Polignac number, because 81655811 - 2² = 81655807 is a prime.

It is a super-3 number, since 3×81655811³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81655813) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2401625 + ... + 2401658.

It is an arithmetic number, because the mean of its divisors is an integer number (21614778).

Almost surely, 2^81655811 is an apocalyptic number.

81655811 is a deficient number, since it is larger than the sum of its proper divisors (4803301).

81655811 is a wasteful number, since it uses less digits than its factorization.

81655811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4803300.

The product of its digits is 9600, while the sum is 35.

The square root of 81655811 is about 9036.3604952436. The cubic root of 81655811 is about 433.8394413412.

The spelling of 81655811 in words is "eighty-one million, six hundred fifty-five thousand, eight hundred eleven".