221561766 has 12 divisors (see below), whose sum is σ = 480050532. Its totient is φ = 73853916.

The previous prime is 221561707. The next prime is 221561771. The reversal of 221561766 is 667165122.

It is a happy number.

221561766 is a `hidden beast` number, since 2 + 21 + 561 + 76 + 6 = 666.

221561766 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 221561766.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6154476 + ... + 6154511.

It is an arithmetic number, because the mean of its divisors is an integer number (40004211).

Almost surely, 2^221561766 is an apocalyptic number.

221561766 is an abundant number, since it is smaller than the sum of its proper divisors (258488766).

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

221561766 is a wasteful number, since it uses less digits than its factorization.

221561766 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12308995 (or 12308992 counting only the distinct ones).

The product of its digits is 30240, while the sum is 36.

The square root of 221561766 is about 14884.9509908498. The cubic root of 221561766 is about 605.1062045185.

The spelling of 221561766 in words is "two hundred twenty-one million, five hundred sixty-one thousand, seven hundred sixty-six".