1216778580 has 36 divisors (see below), whose sum is σ = 3690895572. Its totient is φ = 324474240.

The previous prime is 1216778561. The next prime is 1216778581. The reversal of 1216778580 is 858776121.

It is a happy number.

1216778580 is a `hidden beast` number, since 1 + 2 + 1 + 67 + 7 + 8 + 580 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 474107076 + 742671504 = 21774^2 + 27252^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×1216778580² = 2961100225493632800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216778581) 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, 3379761 + ... + 3380120.

It is an arithmetic number, because the mean of its divisors is an integer number (102524877).

Almost surely, 2^1216778580 is an apocalyptic number.

1216778580 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1216778580 is an abundant number, since it is smaller than the sum of its proper divisors (2474116992).

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

1216778580 is a wasteful number, since it uses less digits than its factorization.

1216778580 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6759896 (or 6759891 counting only the distinct ones).

The product of its (nonzero) digits is 188160, while the sum is 45.

The square root of 1216778580 is about 34882.3534183117. The cubic root of 1216778580 is about 1067.5884139741.

The spelling of 1216778580 in words is "one billion, two hundred sixteen million, seven hundred seventy-eight thousand, five hundred eighty".