66856999 has 4 divisors (see below), whose sum is σ = 72934920. Its totient is φ = 60779080.

The previous prime is 66856973. The next prime is 66857027. The reversal of 66856999 is 99965866.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 66856999 - 2⁷ = 66856871 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66856939) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3038944 + ... + 3038965.

It is an arithmetic number, because the mean of its divisors is an integer number (18233730).

Almost surely, 2^66856999 is an apocalyptic number.

66856999 is a deficient number, since it is larger than the sum of its proper divisors (6077921).

66856999 is a wasteful number, since it uses less digits than its factorization.

66856999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6077920.

The product of its digits is 6298560, while the sum is 58.

The square root of 66856999 is about 8176.6129295693. The cubic root of 66856999 is about 405.8656462917.

The spelling of 66856999 in words is "sixty-six million, eight hundred fifty-six thousand, nine hundred ninety-nine".