261555816 has 32 divisors (see below), whose sum is σ = 682320960. Its totient is φ = 83394432.

The previous prime is 261555797. The next prime is 261555823. The reversal of 261555816 is 618555162.

261555816 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×261555816² = 136822889766851712, which contains 22 as substring.

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, 236365 + ... + 237468.

It is an arithmetic number, because the mean of its divisors is an integer number (21322530).

Almost surely, 2^261555816 is an apocalyptic number.

It is an amenable number.

261555816 is an abundant number, since it is smaller than the sum of its proper divisors (420765144).

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

261555816 is a wasteful number, since it uses less digits than its factorization.

261555816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 473865 (or 473861 counting only the distinct ones).

The product of its digits is 72000, while the sum is 39.

The square root of 261555816 is about 16172.6873462638. The cubic root of 261555816 is about 639.5209761877.

The spelling of 261555816 in words is "two hundred sixty-one million, five hundred fifty-five thousand, eight hundred sixteen".