261563778 has 24 divisors (see below), whose sum is σ = 647682048. Its totient is φ = 74732472.

The previous prime is 261563777. The next prime is 261563801. The reversal of 261563778 is 877365162.

261563778 is a `hidden beast` number, since 2 + 6 + 1 + 5 + 637 + 7 + 8 = 666.

261563778 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (261563777) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1037826 + ... + 1038077.

It is an arithmetic number, because the mean of its divisors is an integer number (26986752).

Almost surely, 2^261563778 is an apocalyptic number.

261563778 is an abundant number, since it is smaller than the sum of its proper divisors (386118270).

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

261563778 is a wasteful number, since it uses less digits than its factorization.

261563778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2075918 (or 2075915 counting only the distinct ones).

The product of its digits is 423360, while the sum is 45.

The square root of 261563778 is about 16172.9335001415. The cubic root of 261563778 is about 639.5274653244.

The spelling of 261563778 in words is "two hundred sixty-one million, five hundred sixty-three thousand, seven hundred seventy-eight".