20555504021 has 4 divisors (see below), whose sum is σ = 22136696652. Its totient is φ = 18974311392.

The previous prime is 20555504017. The next prime is 20555504059. The reversal of 20555504021 is 12040555502.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12040555502 = 2 ⋅6020277751.

It can be written as a sum of positive squares in 2 ways, for example, as 1015378225 + 19540125796 = 31865^2 + 139786^2 .

It is a cyclic number.

It is not a de Polignac number, because 20555504021 - 2² = 20555504017 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20555504621) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 790596296 + ... + 790596321.

It is an arithmetic number, because the mean of its divisors is an integer number (5534174163).

Almost surely, 2^20555504021 is an apocalyptic number.

It is an amenable number.

20555504021 is a deficient number, since it is larger than the sum of its proper divisors (1581192631).

20555504021 is a wasteful number, since it uses less digits than its factorization.

20555504021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1581192630.

The product of its (nonzero) digits is 10000, while the sum is 29.

The spelling of 20555504021 in words is "twenty billion, five hundred fifty-five million, five hundred four thousand, twenty-one".