261978166 has 8 divisors (see below), whose sum is σ = 398350584. Its totient is φ = 129194640.

The previous prime is 261978161. The next prime is 261978169. The reversal of 261978166 is 661879162.

261978166 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261978161) 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 3 ways as a sum of consecutive naturals, for example, 897040 + ... + 897331.

It is an arithmetic number, because the mean of its divisors is an integer number (49793823).

Almost surely, 2^261978166 is an apocalyptic number.

261978166 is a deficient number, since it is larger than the sum of its proper divisors (136372418).

261978166 is a wasteful number, since it uses less digits than its factorization.

261978166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1794446.

The product of its digits is 217728, while the sum is 46.

The square root of 261978166 is about 16185.7395876741. The cubic root of 261978166 is about 639.8650154773.

It can be divided in two parts, 261978 and 166, that added together give a 18-th power (262144 = 2¹⁸).

The spelling of 261978166 in words is "two hundred sixty-one million, nine hundred seventy-eight thousand, one hundred sixty-six".