66778621 has 24 divisors (see below), whose sum is σ = 84779520. Its totient is φ = 52127712.

The previous prime is 66778609. The next prime is 66778631. The reversal of 66778621 is 12687766.

It is not a de Polignac number, because 66778621 - 2¹⁵ = 66745853 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66778631) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 49660 + ... + 50986.

It is an arithmetic number, because the mean of its divisors is an integer number (3532480).

Almost surely, 2^66778621 is an apocalyptic number.

It is an amenable number.

66778621 is a deficient number, since it is larger than the sum of its proper divisors (18000899).

66778621 is a wasteful number, since it uses less digits than its factorization.

66778621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1433 (or 1426 counting only the distinct ones).

The product of its digits is 169344, while the sum is 43.

The square root of 66778621 is about 8171.8187082191. The cubic root of 66778621 is about 405.7069823916.

The spelling of 66778621 in words is "sixty-six million, seven hundred seventy-eight thousand, six hundred twenty-one".