20661266505 has 64 divisors (see below), whose sum is σ = 38432268288. Its totient is φ = 9378082560.

The previous prime is 20661266473. The next prime is 20661266513. The reversal of 20661266505 is 50566216602.

It is a happy number.

It is not a de Polignac number, because 20661266505 - 2⁵ = 20661266473 is a prime.

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, 120447 + ... + 236283.

It is an arithmetic number, because the mean of its divisors is an integer number (600504192).

Almost surely, 2^20661266505 is an apocalyptic number.

It is an amenable number.

20661266505 is a deficient number, since it is larger than the sum of its proper divisors (17771001783).

20661266505 is a wasteful number, since it uses less digits than its factorization.

20661266505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115926.

The product of its (nonzero) digits is 129600, while the sum is 39.

The spelling of 20661266505 in words is "twenty billion, six hundred sixty-one million, two hundred sixty-six thousand, five hundred five".