20516661866 has 16 divisors (see below), whose sum is σ = 31400134920. Its totient is φ = 10052044800.

The previous prime is 20516661799. The next prime is 20516661881. The reversal of 20516661866 is 66816661502.

It can be written as a sum of positive squares in 4 ways, for example, as 20457294841 + 59367025 = 143029^2 + 7705^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 20516661866.

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, 503951 + ... + 543138.

Almost surely, 2^20516661866 is an apocalyptic number.

20516661866 is a deficient number, since it is larger than the sum of its proper divisors (10883473054).

20516661866 is a wasteful number, since it uses less digits than its factorization.

20516661866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1047289.

The product of its (nonzero) digits is 622080, while the sum is 47.

The spelling of 20516661866 in words is "twenty billion, five hundred sixteen million, six hundred sixty-one thousand, eight hundred sixty-six".