261315137664 has 256 divisors, whose sum is σ = 911816352000. Its totient is φ = 72086740992.

The previous prime is 261315137651. The next prime is 261315137669. The reversal of 261315137664 is 466731513162.

261315137664 is a `hidden beast` number, since 2 + 6 + 1 + 3 + 1 + 513 + 76 + 64 = 666.

It is not an unprimeable number, because it can be changed into a prime (261315137669) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 515332 + ... + 887804.

It is an arithmetic number, because the mean of its divisors is an integer number (3561782625).

Almost surely, 2^261315137664 is an apocalyptic number.

261315137664 is a gapful number since it is divisible by the number (24) 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 261315137664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (455908176000).

261315137664 is an abundant number, since it is smaller than the sum of its proper divisors (650501214336).

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

261315137664 is a wasteful number, since it uses less digits than its factorization.

261315137664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 372532 (or 372514 counting only the distinct ones).

The product of its digits is 544320, while the sum is 45.

The spelling of 261315137664 in words is "two hundred sixty-one billion, three hundred fifteen million, one hundred thirty-seven thousand, six hundred sixty-four".