6666391826 has 4 divisors (see below), whose sum is σ = 9999587742. Its totient is φ = 3333195912.

The previous prime is 6666391819. The next prime is 6666391859. The reversal of 6666391826 is 6281936666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6281936666 = 2 ⋅3140968333.

It can be written as a sum of positive squares in only one way, i.e., 6037134601 + 629257225 = 77699^2 + 25085^2 .

It is a super-2 number, since 2×6666391826² = 88881559955519228552, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1666597955 + ... + 1666597958.

Almost surely, 2^6666391826 is an apocalyptic number.

6666391826 is a deficient number, since it is larger than the sum of its proper divisors (3333195916).

6666391826 is a wasteful number, since it uses less digits than its factorization.

6666391826 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3333195915.

The product of its digits is 3359232, while the sum is 53.

The square root of 6666391826 is about 81647.9750269411. The cubic root of 6666391826 is about 1882.0461939097.

The spelling of 6666391826 in words is "six billion, six hundred sixty-six million, three hundred ninety-one thousand, eight hundred twenty-six".