66666399 has 16 divisors (see below), whose sum is σ = 91975680. Its totient is φ = 42907680.

The previous prime is 66666371. The next prime is 66666409. The reversal of 66666399 is 99366666.

It is not a de Polignac number, because 66666399 - 2¹⁷ = 66535327 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66666319) 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, 66369 + ... + 67365.

It is an arithmetic number, because the mean of its divisors is an integer number (5748480).

Almost surely, 2^66666399 is an apocalyptic number.

66666399 is a deficient number, since it is larger than the sum of its proper divisors (25309281).

66666399 is a wasteful number, since it uses less digits than its factorization.

66666399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1750.

The product of its digits is 1889568, while the sum is 51.

The square root of 66666399 is about 8164.9494180919. The cubic root of 66666399 is about 405.4795903699.

The spelling of 66666399 in words is "sixty-six million, six hundred sixty-six thousand, three hundred ninety-nine".