66699665 has 8 divisors (see below), whose sum is σ = 81901248. Its totient is φ = 52118640.

The previous prime is 66699649. The next prime is 66699667. The reversal of 66699665 is 56699666.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 66699665 - 2⁴ = 66699649 is a prime.

It is a super-2 number, since 2×66699665² = 8897690622224450, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66699667) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 154901 + ... + 155330.

It is an arithmetic number, because the mean of its divisors is an integer number (10237656).

Almost surely, 2^66699665 is an apocalyptic number.

It is an amenable number.

66699665 is a deficient number, since it is larger than the sum of its proper divisors (15201583).

66699665 is a wasteful number, since it uses less digits than its factorization.

66699665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 310279.

The product of its digits is 3149280, while the sum is 53.

The square root of 66699665 is about 8166.9862862625. The cubic root of 66699665 is about 405.5470228461.

Subtracting from 66699665 its reverse (56699666), we obtain a palindrome (9999999).

The spelling of 66699665 in words is "sixty-six million, six hundred ninety-nine thousand, six hundred sixty-five".