201561564666 has 128 divisors (see below), whose sum is σ = 506194292736. Its totient is φ = 51980129280.

The previous prime is 201561564613. The next prime is 201561564679. The reversal of 201561564666 is 666465165102.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 38514786 + ... + 38520018.

It is an arithmetic number, because the mean of its divisors is an integer number (3954642912).

Almost surely, 2^201561564666 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 201561564666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (253097146368).

201561564666 is an abundant number, since it is smaller than the sum of its proper divisors (304632728070).

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

201561564666 is a wasteful number, since it uses less digits than its factorization.

201561564666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5836.

The product of its (nonzero) digits is 1555200, while the sum is 48.

The spelling of 201561564666 in words is "two hundred one billion, five hundred sixty-one million, five hundred sixty-four thousand, six hundred sixty-six".