20891966505489 has 24 divisors (see below), whose sum is σ = 30651489348480. Its totient is φ = 13709872734912.

The previous prime is 20891966505479. The next prime is 20891966505497. The reversal of 20891966505489 is 98450566919802.

20891966505489 is a `hidden beast` number, since 2 + 0 + 8 + 9 + 1 + 96 + 6 + 50 + 5 + 489 = 666.

It is not a de Polignac number, because 20891966505489 - 2²³ = 20891958116881 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20891966505479) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 31278909 + ... + 31939850.

It is an arithmetic number, because the mean of its divisors is an integer number (1277145389520).

Almost surely, 2^{20891966505489} is an apocalyptic number.

It is an amenable number.

20891966505489 is a deficient number, since it is larger than the sum of its proper divisors (9759522842991).

20891966505489 is a wasteful number, since it uses less digits than its factorization.

20891966505489 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63219341 (or 63219338 counting only the distinct ones).

The product of its (nonzero) digits is 335923200, while the sum is 72.

The spelling of 20891966505489 in words is "twenty trillion, eight hundred ninety-one billion, nine hundred sixty-six million, five hundred five thousand, four hundred eighty-nine".