261663630 has 96 divisors (see below), whose sum is σ = 681740064. Its totient is φ = 64219392.

The previous prime is 261663601. The next prime is 261663631. The reversal of 261663630 is 36366162.

It is a happy number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 261663591 and 261663600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261663631) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 400384 + ... + 401036.

It is an arithmetic number, because the mean of its divisors is an integer number (7101459).

Almost surely, 2^261663630 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261663630, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (340870032).

261663630 is an abundant number, since it is smaller than the sum of its proper divisors (420076434).

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

261663630 is a wasteful number, since it uses less digits than its factorization.

261663630 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 738 (or 719 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 33.

The square root of 261663630 is about 16176.0202151209. The cubic root of 261663630 is about 639.6088348636.

The spelling of 261663630 in words is "two hundred sixty-one million, six hundred sixty-three thousand, six hundred thirty".