1261778868 has 36 divisors (see below), whose sum is σ = 3645139680. Its totient is φ = 360508176.

The previous prime is 1261778867. The next prime is 1261778927. The reversal of 1261778868 is 8688771621.

It is a happy number.

1261778868 is a `hidden beast` number, since 12 + 617 + 7 + 8 + 8 + 6 + 8 = 666.

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

It is a super-2 number, since 2×1261778868² = 3184171823462722848, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261778863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2503278 + ... + 2503781.

It is an arithmetic number, because the mean of its divisors is an integer number (101253880).

Almost surely, 2^1261778868 is an apocalyptic number.

1261778868 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is an amenable number.

1261778868 is an abundant number, since it is smaller than the sum of its proper divisors (2383360812).

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

1261778868 is a wasteful number, since it uses less digits than its factorization.

1261778868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5007076 (or 5007071 counting only the distinct ones).

The product of its digits is 1806336, while the sum is 54.

The square root of 1261778868 is about 35521.5268252929. The cubic root of 1261778868 is about 1080.5903459726.

The spelling of 1261778868 in words is "one billion, two hundred sixty-one million, seven hundred seventy-eight thousand, eight hundred sixty-eight".