261220520166 has 8 divisors (see below), whose sum is σ = 522441040344. Its totient is φ = 87073506720.

The previous prime is 261220520161. The next prime is 261220520173. The reversal of 261220520166 is 661025022162.

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

261220520166 is an admirable number.

It is a super-2 number, since 2×261220520166² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261220520161) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21768376675 + ... + 21768376686.

It is an arithmetic number, because the mean of its divisors is an integer number (65305130043).

Almost surely, 2^261220520166 is an apocalyptic number.

261220520166 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

261220520166 is a wasteful number, since it uses less digits than its factorization.

261220520166 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43536753366.

The product of its (nonzero) digits is 17280, while the sum is 33.

The spelling of 261220520166 in words is "two hundred sixty-one billion, two hundred twenty million, five hundred twenty thousand, one hundred sixty-six".