21020819955 has 16 divisors (see below), whose sum is σ = 35403486720. Its totient is φ = 10621045728.

The previous prime is 21020819951. The next prime is 21020819999. The reversal of 21020819955 is 55991802012.

It is not a de Polignac number, because 21020819955 - 2² = 21020819951 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21020819951) 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 15 ways as a sum of consecutive naturals, for example, 36878347 + ... + 36878916.

It is an arithmetic number, because the mean of its divisors is an integer number (2212717920).

Almost surely, 2^21020819955 is an apocalyptic number.

21020819955 is a deficient number, since it is larger than the sum of its proper divisors (14382666765).

21020819955 is a wasteful number, since it uses less digits than its factorization.

21020819955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73757290.

The product of its (nonzero) digits is 64800, while the sum is 42.

The spelling of 21020819955 in words is "twenty-one billion, twenty million, eight hundred nineteen thousand, nine hundred fifty-five".