261657240 has 64 divisors (see below), whose sum is σ = 845359200. Its totient is φ = 64407552.

The previous prime is 261657239. The next prime is 261657257. The reversal of 261657240 is 42756162.

It is a super-2 number, since 2×261657240² = 136929022488835200, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 82305 + ... + 85424.

Almost surely, 2^261657240 is an apocalyptic number.

261657240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261657240 is an abundant number, since it is smaller than the sum of its proper divisors (583701960).

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

261657240 is a wasteful number, since it uses less digits than its factorization.

261657240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167756 (or 167752 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 33.

The square root of 261657240 is about 16175.8226993251. The cubic root of 261657240 is about 639.6036282634.

The spelling of 261657240 in words is "two hundred sixty-one million, six hundred fifty-seven thousand, two hundred forty".