261920355840 has 1600 divisors, whose sum is σ = 1126453027392. Its totient is φ = 57808650240.

The previous prime is 261920355817. The next prime is 261920355859. The reversal of 261920355840 is 48553029162.

261920355840 is a `hidden beast` number, since 2 + 6 + 1 + 92 + 0 + 3 + 558 + 4 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 159 ways as a sum of consecutive naturals, for example, 3587950044 + ... + 3587950116.

Almost surely, 2^261920355840 is an apocalyptic number.

261920355840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261920355840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (563226513696).

261920355840 is an abundant number, since it is smaller than the sum of its proper divisors (864532671552).

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

261920355840 is an equidigital number, since it uses as much as digits as its factorization.

261920355840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154 (or 107 counting only the distinct ones).

The product of its (nonzero) digits is 518400, while the sum is 45.

The spelling of 261920355840 in words is "two hundred sixty-one billion, nine hundred twenty million, three hundred fifty-five thousand, eight hundred forty".