66801991959 has 24 divisors (see below), whose sum is σ = 101214277632. Its totient is φ = 42375318480.

The previous prime is 66801991951. The next prime is 66801991967. The reversal of 66801991959 is 95919910866.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (66801991951) and next prime (66801991967).

It is not a de Polignac number, because 66801991959 - 2³ = 66801991951 is a prime.

It is a super-2 number, since 2×66801991959² (a number of 22 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 66801991896 and 66801991905.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66801991951) 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 23 ways as a sum of consecutive naturals, for example, 805267 + ... + 884340.

It is an arithmetic number, because the mean of its divisors is an integer number (4217261568).

Almost surely, 2^66801991959 is an apocalyptic number.

66801991959 is a gapful number since it is divisible by the number (69) formed by its first and last digit.

66801991959 is a deficient number, since it is larger than the sum of its proper divisors (34412285673).

66801991959 is a wasteful number, since it uses less digits than its factorization.

66801991959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1689827 (or 1689824 counting only the distinct ones).

The product of its (nonzero) digits is 9447840, while the sum is 63.

The spelling of 66801991959 in words is "sixty-six billion, eight hundred one million, nine hundred ninety-one thousand, nine hundred fifty-nine".