20661516511550 has 48 divisors (see below), whose sum is σ = 42211903800960. Its totient is φ = 7489208723040.

The previous prime is 20661516511507. The next prime is 20661516511609. The reversal of 20661516511550 is 5511561516602.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 472781732 + ... + 472825431.

It is an arithmetic number, because the mean of its divisors is an integer number (879414662520).

Almost surely, 2^{20661516511550} is an apocalyptic number.

20661516511550 is an abundant number, since it is smaller than the sum of its proper divisors (21550387289410).

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

20661516511550 is a wasteful number, since it uses less digits than its factorization.

20661516511550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 945607217 (or 945607212 counting only the distinct ones).

The product of its (nonzero) digits is 270000, while the sum is 44.

The spelling of 20661516511550 in words is "twenty trillion, six hundred sixty-one billion, five hundred sixteen million, five hundred eleven thousand, five hundred fifty".