261666374641421 has 16 divisors (see below), whose sum is σ = 262476600781824. Its totient is φ = 260857267832064.

The previous prime is 261666374641391. The next prime is 261666374641433. The reversal of 261666374641421 is 124146473666162.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261666374641421 is a prime.

It is a super-3 number, since 3×261666374641421³ (a number of 44 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261666374541421) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6093320276 + ... + 6093363218.

It is an arithmetic number, because the mean of its divisors is an integer number (16404787548864).

Almost surely, 2^{261666374641421} is an apocalyptic number.

It is an amenable number.

261666374641421 is a deficient number, since it is larger than the sum of its proper divisors (810226140403).

261666374641421 is a wasteful number, since it uses less digits than its factorization.

261666374641421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55540.

The product of its digits is 41803776, while the sum is 59.

The spelling of 261666374641421 in words is "two hundred sixty-one trillion, six hundred sixty-six billion, three hundred seventy-four million, six hundred forty-one thousand, four hundred twenty-one".