81661151 has 16 divisors (see below), whose sum is σ = 96314400. Its totient is φ = 68257920.

The previous prime is 81661123. The next prime is 81661159. The reversal of 81661151 is 15116618.

It is a cyclic number.

It is not a de Polignac number, because 81661151 - 2⁶ = 81661087 is a prime.

It is a super-3 number, since 3×81661151³ (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 (81661159) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 40925 + ... + 42873.

It is an arithmetic number, because the mean of its divisors is an integer number (6019650).

Almost surely, 2^81661151 is an apocalyptic number.

81661151 is a deficient number, since it is larger than the sum of its proper divisors (14653249).

81661151 is a wasteful number, since it uses less digits than its factorization.

81661151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2266.

The product of its digits is 1440, while the sum is 29.

The square root of 81661151 is about 9036.6559633528. The cubic root of 81661151 is about 433.8488983212.

Adding to 81661151 its reverse (15116618), we get a palindrome (96777769).

The spelling of 81661151 in words is "eighty-one million, six hundred sixty-one thousand, one hundred fifty-one".