261488640 has 288 divisors, whose sum is σ = 1006629120. Its totient is φ = 56623104.

The previous prime is 261488609. The next prime is 261488641. The reversal of 261488640 is 46884162.

It is a nialpdrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261488641) 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, 13762551 + ... + 13762569.

It is an arithmetic number, because the mean of its divisors is an integer number (3495240).

Almost surely, 2^261488640 is an apocalyptic number.

261488640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

261488640 is a droll number since its even prime factors and its odd prime factors have the same sum.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261488640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (503314560).

261488640 is an abundant number, since it is smaller than the sum of its proper divisors (745140480).

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

261488640 is an frugal number, since it uses more digits than its factorization.

261488640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68 (or 36 counting only the distinct ones).

The product of its (nonzero) digits is 73728, while the sum is 39.

The square root of 261488640 is about 16170.6103780902. The cubic root of 261488640 is about 639.4662216039.

The spelling of 261488640 in words is "two hundred sixty-one million, four hundred eighty-eight thousand, six hundred forty".