66791778 has 16 divisors (see below), whose sum is σ = 133726656. Its totient is φ = 22240080.

The previous prime is 66791773. The next prime is 66791779. The reversal of 66791778 is 87719766.

It is a happy number.

It is a super-2 number, since 2×66791778² = 8922283216802568, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 66791778.

It is not an unprimeable number, because it can be changed into a prime (66791773) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 675 + ... + 11577.

It is an arithmetic number, because the mean of its divisors is an integer number (8357916).

Almost surely, 2^66791778 is an apocalyptic number.

66791778 is an abundant number, since it is smaller than the sum of its proper divisors (66934878).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66791778 is a wasteful number, since it uses less digits than its factorization.

66791778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11929.

The product of its digits is 889056, while the sum is 51.

The square root of 66791778 is about 8172.6236913246. The cubic root of 66791778 is about 405.7336253309.

The spelling of 66791778 in words is "sixty-six million, seven hundred ninety-one thousand, seven hundred seventy-eight".