261665577540654 has 64 divisors (see below), whose sum is σ = 634327876131840. Its totient is φ = 70338776555520.

The previous prime is 261665577540613. The next prime is 261665577540673. The reversal of 261665577540654 is 456045775566162.

It is a happy number.

It is a super-2 number, since 2×261665577540654² (a number of 30 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (69).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2220230739 + ... + 2220348590.

It is an arithmetic number, because the mean of its divisors is an integer number (9911373064560).

Almost surely, 2^{261665577540654} is an apocalyptic number.

261665577540654 is an abundant number, since it is smaller than the sum of its proper divisors (372662298591186).

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

261665577540654 is a wasteful number, since it uses less digits than its factorization.

261665577540654 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4440579425.

The product of its (nonzero) digits is 1270080000, while the sum is 69.

The spelling of 261665577540654 in words is "two hundred sixty-one trillion, six hundred sixty-five billion, five hundred seventy-seven million, five hundred forty thousand, six hundred fifty-four".