261917780 has 24 divisors (see below), whose sum is σ = 550466952. Its totient is φ = 104683392.

The previous prime is 261917771. The next prime is 261917797. The reversal of 261917780 is 87719162.

261917780 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 87572164 + 174345616 = 9358^2 + 13204^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24554 + ... + 33566.

It is an arithmetic number, because the mean of its divisors is an integer number (22936123).

Almost surely, 2^261917780 is an apocalyptic number.

261917780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261917780 is an abundant number, since it is smaller than the sum of its proper divisors (288549172).

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

261917780 is a wasteful number, since it uses less digits than its factorization.

261917780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10475 (or 10473 counting only the distinct ones).

The product of its (nonzero) digits is 42336, while the sum is 41.

The square root of 261917780 is about 16183.8740726688. The cubic root of 261917780 is about 639.8158487108.

The spelling of 261917780 in words is "two hundred sixty-one million, nine hundred seventeen thousand, seven hundred eighty".