261717640 has 32 divisors (see below), whose sum is σ = 594944280. Its totient is φ = 103606272.

The previous prime is 261717623. The next prime is 261717661. The reversal of 261717640 is 46717162.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 134884996 + 126832644 = 11614^2 + 11262^2 .

It is a super-2 number, since 2×261717640² = 136992246174339200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 261717596 and 261717605.

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, 29847 + ... + 37606.

Almost surely, 2^261717640 is an apocalyptic number.

261717640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261717640 is an abundant number, since it is smaller than the sum of its proper divisors (333226640).

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

261717640 is a wasteful number, since it uses less digits than its factorization.

261717640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67561 (or 67557 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 261717640 is about 16177.6895754616. The cubic root of 261717640 is about 639.6528390642.

The spelling of 261717640 in words is "two hundred sixty-one million, seven hundred seventeen thousand, six hundred forty".