261840720 has 40 divisors (see below), whose sum is σ = 811706976. Its totient is φ = 69824128.

The previous prime is 261840701. The next prime is 261840721. The reversal of 261840720 is 27048162.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261840721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 545262 + ... + 545741.

Almost surely, 2^261840720 is an apocalyptic number.

261840720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261840720 is an abundant number, since it is smaller than the sum of its proper divisors (549866256).

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

261840720 is a wasteful number, since it uses less digits than its factorization.

261840720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1091019 (or 1091013 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 261840720 is about 16181.4931325882. The cubic root of 261840720 is about 639.7530948631.

Adding to 261840720 its reverse (27048162), we get a palindrome (288888882).

The spelling of 261840720 in words is "two hundred sixty-one million, eight hundred forty thousand, seven hundred twenty".