261399240 has 48 divisors (see below), whose sum is σ = 849548700. Its totient is φ = 69706368.

The previous prime is 261399239. The next prime is 261399241. The reversal of 261399240 is 42993162.

261399240 is a `hidden beast` number, since 26 + 1 + 399 + 240 = 666.

It is an interprime number because it is at equal distance from previous prime (261399239) and next prime (261399241).

It can be written as a sum of positive squares in 2 ways, for example, as 253000836 + 8398404 = 15906^2 + 2898^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 261399195 and 261399204.

It is not an unprimeable number, because it can be changed into a prime (261399241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 362695 + ... + 363414.

Almost surely, 2^261399240 is an apocalyptic number.

261399240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261399240 is an abundant number, since it is smaller than the sum of its proper divisors (588149460).

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

261399240 is a wasteful number, since it uses less digits than its factorization.

261399240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 726126 (or 726119 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 36.

The square root of 261399240 is about 16167.8458676473. The cubic root of 261399240 is about 639.3933378813.

The spelling of 261399240 in words is "two hundred sixty-one million, three hundred ninety-nine thousand, two hundred forty".