1221657678 has 24 divisors (see below), whose sum is σ = 2658294288. Its totient is φ = 405470112.

The previous prime is 1221657677. The next prime is 1221657707. The reversal of 1221657678 is 8767561221.

1221657678 is a `hidden beast` number, since 1 + 2 + 2 + 1 + 6 + 576 + 78 = 666.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221657677) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 141450 + ... + 149837.

It is an arithmetic number, because the mean of its divisors is an integer number (110762262).

Almost surely, 2^1221657678 is an apocalyptic number.

1221657678 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1221657678 is an abundant number, since it is smaller than the sum of its proper divisors (1436636610).

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

1221657678 is a wasteful number, since it uses less digits than its factorization.

1221657678 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291528 (or 291525 counting only the distinct ones).

The product of its digits is 282240, while the sum is 45.

The square root of 1221657678 is about 34952.2199294980. The cubic root of 1221657678 is about 1069.0134669216.

The spelling of 1221657678 in words is "one billion, two hundred twenty-one million, six hundred fifty-seven thousand, six hundred seventy-eight".