21050020865 has 16 divisors (see below), whose sum is σ = 27091195200. Its totient is φ = 15652683072.

The previous prime is 21050020853. The next prime is 21050020879. The reversal of 21050020865 is 56802005012.

It is a cyclic number.

It is not a de Polignac number, because 21050020865 - 2²⁶ = 20982912001 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2085335 + ... + 2095404.

It is an arithmetic number, because the mean of its divisors is an integer number (1693199700).

Almost surely, 2^21050020865 is an apocalyptic number.

It is an amenable number.

21050020865 is a deficient number, since it is larger than the sum of its proper divisors (6041174335).

21050020865 is a wasteful number, since it uses less digits than its factorization.

21050020865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4180816.

The product of its (nonzero) digits is 4800, while the sum is 29.

Adding to 21050020865 its reverse (56802005012), we get a palindrome (77852025877).

The spelling of 21050020865 in words is "twenty-one billion, fifty million, twenty thousand, eight hundred sixty-five".