261005664 has 48 divisors (see below), whose sum is σ = 699729408. Its totient is φ = 85149312.

The previous prime is 261005639. The next prime is 261005677. The reversal of 261005664 is 466500162.

It is a tau number, because it is divible by the number of its divisors (48).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24412 + ... + 33435.

It is an arithmetic number, because the mean of its divisors is an integer number (14577696).

Almost surely, 2^261005664 is an apocalyptic number.

261005664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

261005664 is an abundant number, since it is smaller than the sum of its proper divisors (438723744).

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

261005664 is a wasteful number, since it uses less digits than its factorization.

261005664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57907 (or 57899 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 261005664 is about 16155.6697168517. The cubic root of 261005664 is about 639.0722756407.

The spelling of 261005664 in words is "two hundred sixty-one million, five thousand, six hundred sixty-four".