20987266517 has 4 divisors (see below), whose sum is σ = 23985447456. Its totient is φ = 17989085580.

The previous prime is 20987266499. The next prime is 20987266519. The reversal of 20987266517 is 71566278902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20987266517 - 2⁶ = 20987266453 is a prime.

It is a super-2 number, since 2×20987266517² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20987266519) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1499090459 + ... + 1499090472.

It is an arithmetic number, because the mean of its divisors is an integer number (5996361864).

Almost surely, 2^20987266517 is an apocalyptic number.

It is an amenable number.

20987266517 is a deficient number, since it is larger than the sum of its proper divisors (2998180939).

20987266517 is an equidigital number, since it uses as much as digits as its factorization.

20987266517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2998180938.

The product of its (nonzero) digits is 2540160, while the sum is 53.

The spelling of 20987266517 in words is "twenty billion, nine hundred eighty-seven million, two hundred sixty-six thousand, five hundred seventeen".