261506987640378 has 24 divisors (see below), whose sum is σ = 566600517174900. Its totient is φ = 87168681425664.

The previous prime is 261506987640373. The next prime is 261506987640407. The reversal of 261506987640378 is 873046789605162.

261506987640378 is a `hidden beast` number, since 2 + 6 + 1 + 506 + 9 + 8 + 7 + 6 + 40 + 3 + 78 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 173432385213129 + 88074602427249 = 13169373^2 + 9384807^2 .

It is not an unprimeable number, because it can be changed into a prime (261506987640373) 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, 21048793 + ... + 31081596.

It is a 1-persistent number, because it is pandigital, but 2⋅261506987640378 = 523013975280756 is not.

Almost surely, 2^{261506987640378} is an apocalyptic number.

261506987640378 is an abundant number, since it is smaller than the sum of its proper divisors (305093529534522).

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

261506987640378 is a wasteful number, since it uses less digits than its factorization.

261506987640378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52409086 (or 52409083 counting only the distinct ones).

The product of its (nonzero) digits is 731566080, while the sum is 72.

The spelling of 261506987640378 in words is "two hundred sixty-one trillion, five hundred six billion, nine hundred eighty-seven million, six hundred forty thousand, three hundred seventy-eight".