261930027681 has 27 divisors (see below), whose sum is σ = 440131779633. Its totient is φ = 149668160040.

The previous prime is 261930027673. The next prime is 261930027721. The reversal of 261930027681 is 186720039162.

The square root of 261930027681 is 511791.

It is a perfect power (a square), and thus also a powerful number.

261930027681 is a `hidden beast` number, since 2 + 619 + 3 + 0 + 0 + 27 + 6 + 8 + 1 = 666.

It is not a de Polignac number, because 261930027681 - 2³ = 261930027673 is a prime.

It is a super-2 number, since 2×261930027681² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (261930027641) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 10735426 + ... + 10759796.

Almost surely, 2^261930027681 is an apocalyptic number.

261930027681 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

261930027681 is the 511791-st square number.

261930027681 is the 255896-th centered octagonal number.

It is an amenable number.

261930027681 is a deficient number, since it is larger than the sum of its proper divisors (178201751952).

261930027681 is an frugal number, since it uses more digits than its factorization.

261930027681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48762 (or 24381 counting only the distinct ones).

The product of its (nonzero) digits is 217728, while the sum is 45.

The spelling of 261930027681 in words is "two hundred sixty-one billion, nine hundred thirty million, twenty-seven thousand, six hundred eighty-one".