1066639991 has 16 divisors (see below), whose sum is σ = 1095494400. Its totient is φ = 1038312000.

The previous prime is 1066639967. The next prime is 1066640009. The reversal of 1066639991 is 1999366601.

It is a happy number.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1066639991 is a prime.

It is a super-2 number, since 2×1066639991² = 2275441740800960162, which contains 22 as substring.

It is a Smith number, since the sum of its digits (50) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1066639901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1867736 + ... + 1868306.

It is an arithmetic number, because the mean of its divisors is an integer number (68468400).

Almost surely, 2^1066639991 is an apocalyptic number.

1066639991 is a deficient number, since it is larger than the sum of its proper divisors (28854409).

1066639991 is a wasteful number, since it uses less digits than its factorization.

1066639991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 950.

The product of its (nonzero) digits is 472392, while the sum is 50.

The square root of 1066639991 is about 32659.4548484815. The cubic root of 1066639991 is about 1021.7373923642.

The spelling of 1066639991 in words is "one billion, sixty-six million, six hundred thirty-nine thousand, nine hundred ninety-one".