81331666 has 32 divisors (see below), whose sum is σ = 140616000. Its totient is φ = 34966080.

The previous prime is 81331651. The next prime is 81331669. The reversal of 81331666 is 66613318.

It is a happy number.

It is a super-2 number, since 2×81331666² = 13229679788671112, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81331669) 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, 28785 + ... + 31483.

It is an arithmetic number, because the mean of its divisors is an integer number (4394250).

Almost surely, 2^81331666 is an apocalyptic number.

81331666 is a deficient number, since it is larger than the sum of its proper divisors (59284334).

81331666 is a wasteful number, since it uses less digits than its factorization.

81331666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2794.

The product of its digits is 15552, while the sum is 34.

The square root of 81331666 is about 9018.4070655521. The cubic root of 81331666 is about 433.2646164541.

The spelling of 81331666 in words is "eighty-one million, three hundred thirty-one thousand, six hundred sixty-six".