261501240 has 384 divisors, whose sum is σ = 1075576320. Its totient is φ = 49996800.

The previous prime is 261501223. The next prime is 261501269. The reversal of 261501240 is 42105162.

261501240 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Cunningham number, because it is equal to 16171²-1.

It is a Harshad number since it is a multiple of its sum of digits (21).

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, 840685 + ... + 840995.

It is an arithmetic number, because the mean of its divisors is an integer number (2800980).

Almost surely, 2^261501240 is an apocalyptic number.

261501240 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 261501240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (537788160).

261501240 is an abundant number, since it is smaller than the sum of its proper divisors (814075080).

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

261501240 is a wasteful number, since it uses less digits than its factorization.

261501240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 363 (or 352 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 261501240 is about 16170.9999690805. Note that the first 4 decimals coincide. The cubic root of 261501240 is about 639.4764924707.

It can be divided in two parts, 261 and 501240, that added together give a triangular number (501501 = T₁₀₀₁).

The spelling of 261501240 in words is "two hundred sixty-one million, five hundred one thousand, two hundred forty".