261957780 has 192 divisors, whose sum is σ = 957089280. Its totient is φ = 58226688.

The previous prime is 261957779. The next prime is 261957791. The reversal of 261957780 is 87759162.

261957780 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 138924 + ... + 140796.

It is an arithmetic number, because the mean of its divisors is an integer number (4984840).

Almost surely, 2^261957780 is an apocalyptic number.

261957780 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 261957780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (478544640).

261957780 is an abundant number, since it is smaller than the sum of its proper divisors (695131500).

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

261957780 is a wasteful number, since it uses less digits than its factorization.

261957780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1935 (or 1927 counting only the distinct ones).

The product of its (nonzero) digits is 211680, while the sum is 45.

The square root of 261957780 is about 16185.1098235384. The cubic root of 261957780 is about 639.8484178771.

The spelling of 261957780 in words is "two hundred sixty-one million, nine hundred fifty-seven thousand, seven hundred eighty".