81666099 has 12 divisors (see below), whose sum is σ = 119723656. Its totient is φ = 53631072.

The previous prime is 81666071. The next prime is 81666131. The reversal of 81666099 is 99066618.

It is not a de Polignac number, because 81666099 - 2¹³ = 81657907 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81666019) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 67114 + ... + 68319.

Almost surely, 2^81666099 is an apocalyptic number.

81666099 is a deficient number, since it is larger than the sum of its proper divisors (38057557).

81666099 is a wasteful number, since it uses less digits than its factorization.

81666099 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135506 (or 135503 counting only the distinct ones).

The product of its (nonzero) digits is 139968, while the sum is 45.

The square root of 81666099 is about 9036.9297330454. The cubic root of 81666099 is about 433.8576607130.

It can be divided in two parts, 8166609 and 9, that added together give a palindrome (8166618).

The spelling of 81666099 in words is "eighty-one million, six hundred sixty-six thousand, ninety-nine".