261399057984 has 231 divisors, whose sum is σ = 781035916843. Its totient is φ = 86801715072.

The previous prime is 261399057971. The next prime is 261399057991. The reversal of 261399057984 is 489750993162.

The square root of 261399057984 is 511272.

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

261399057984 is a `hidden beast` number, since 2 + 613 + 9 + 9 + 0 + 5 + 7 + 9 + 8 + 4 = 666.

It is a Duffinian number.

It is an unprimeable number.

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 32 ways as a sum of consecutive naturals, for example, 993912637 + ... + 993912899.

It is a 1-persistent number, because it is pandigital, but 2⋅261399057984 = 522798115968 is not.

Almost surely, 2^261399057984 is an apocalyptic number.

261399057984 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

261399057984 is the 511272-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261399057984

261399057984 is an abundant number, since it is smaller than the sum of its proper divisors (519636858859).

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

261399057984 is an frugal number, since it uses more digits than its factorization.

261399057984 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 568 (or 268 counting only the distinct ones).

The product of its (nonzero) digits is 29393280, while the sum is 63.

The spelling of 261399057984 in words is "two hundred sixty-one billion, three hundred ninety-nine million, fifty-seven thousand, nine hundred eighty-four".