261631440 has 480 divisors, whose sum is σ = 1093787136. Its totient is φ = 54743040.

The previous prime is 261631427. The next prime is 261631453. The reversal of 261631440 is 44136162.

261631440 is a `hidden beast` number, since 2 + 616 + 3 + 1 + 4 + 40 = 666.

261631440 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (261631427) and next prime (261631453).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 4289010 + ... + 4289070.

Almost surely, 2^261631440 is an apocalyptic number.

261631440 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 261631440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (546893568).

261631440 is an abundant number, since it is smaller than the sum of its proper divisors (832155696).

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

261631440 is a wasteful number, since it uses less digits than its factorization.

261631440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147 (or 138 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 261631440 is about 16175.0251931798. The cubic root of 261631440 is about 639.5826054474.

The spelling of 261631440 in words is "two hundred sixty-one million, six hundred thirty-one thousand, four hundred forty".