1217781378 has 56 divisors (see below), whose sum is σ = 2987772336. Its totient is φ = 369019800.

The previous prime is 1217781377. The next prime is 1217781379. The reversal of 1217781378 is 8731877121.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1217781377) and next prime (1217781379).

It is not an unprimeable number, because it can be changed into a prime (1217781373) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 21928 + ... + 54003.

Almost surely, 2^1217781378 is an apocalyptic number.

1217781378 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1217781378 is an abundant number, since it is smaller than the sum of its proper divisors (1769990958).

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

1217781378 is an equidigital number, since it uses as much as digits as its factorization.

1217781378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75962 (or 75947 counting only the distinct ones).

The product of its digits is 131712, while the sum is 45.

The square root of 1217781378 is about 34896.7244594675. The cubic root of 1217781378 is about 1067.8816148288.

The spelling of 1217781378 in words is "one billion, two hundred seventeen million, seven hundred eighty-one thousand, three hundred seventy-eight".