261681240906 has 24 divisors (see below), whose sum is σ = 567968997024. Its totient is φ = 87074314920.

The previous prime is 261681240889. The next prime is 261681241027. The reversal of 261681240906 is 609042186162.

261681240906 is a `hidden beast` number, since 2 + 616 + 8 + 1 + 24 + 0 + 9 + 0 + 6 = 666.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12719886 + ... + 12740441.

It is an arithmetic number, because the mean of its divisors is an integer number (23665374876).

Almost surely, 2^261681240906 is an apocalyptic number.

261681240906 is an abundant number, since it is smaller than the sum of its proper divisors (306287756118).

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

261681240906 is a wasteful number, since it uses less digits than its factorization.

261681240906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25460906 (or 25460903 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 45.

The spelling of 261681240906 in words is "two hundred sixty-one billion, six hundred eighty-one million, two hundred forty thousand, nine hundred six".