261539515440 has 640 divisors, whose sum is σ = 1092015820800. Its totient is φ = 56239349760.

The previous prime is 261539515423. The next prime is 261539515441. The reversal of 261539515440 is 44515935162.

It is a happy number.

261539515440 is a `hidden beast` number, since 2 + 6 + 1 + 53 + 9 + 51 + 544 + 0 = 666.

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

It is not an unprimeable number, because it can be changed into a prime (261539515441) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 21207196 + ... + 21219524.

It is an arithmetic number, because the mean of its divisors is an integer number (1706274720).

Almost surely, 2^261539515440 is an apocalyptic number.

261539515440 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 261539515440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (546007910400).

261539515440 is an abundant number, since it is smaller than the sum of its proper divisors (830476305360).

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

261539515440 is a wasteful number, since it uses less digits than its factorization.

261539515440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12442 (or 12430 counting only the distinct ones).

The product of its (nonzero) digits is 648000, while the sum is 45.

The spelling of 261539515440 in words is "two hundred sixty-one billion, five hundred thirty-nine million, five hundred fifteen thousand, four hundred forty".