21004204555 has 16 divisors (see below), whose sum is σ = 26372634624. Its totient is φ = 16028955360.

The previous prime is 21004204541. The next prime is 21004204567. The reversal of 21004204555 is 55540240012.

It is not a de Polignac number, because 21004204555 - 2²⁵ = 20970650123 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 206631 + ... + 291040.

It is an arithmetic number, because the mean of its divisors is an integer number (1648289664).

Almost surely, 2^21004204555 is an apocalyptic number.

21004204555 is a deficient number, since it is larger than the sum of its proper divisors (5368430069).

21004204555 is a wasteful number, since it uses less digits than its factorization.

21004204555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 498066.

The product of its (nonzero) digits is 8000, while the sum is 28.

Adding to 21004204555 its reverse (55540240012), we get a palindrome (76544444567).

The spelling of 21004204555 in words is "twenty-one billion, four million, two hundred four thousand, five hundred fifty-five".