21204499816 has 8 divisors (see below), whose sum is σ = 39758437170. Its totient is φ = 10602249904.

The previous prime is 21204499807. The next prime is 21204499819. The reversal of 21204499816 is 61899440212.

It can be written as a sum of positive squares in only one way, i.e., 19896230916 + 1308268900 = 141054^2 + 36170^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a hoax number, since the sum of its digits (46) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21204499819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1325281231 + ... + 1325281246.

Almost surely, 2^21204499816 is an apocalyptic number.

It is an amenable number.

21204499816 is a deficient number, since it is larger than the sum of its proper divisors (18553937354).

21204499816 is a wasteful number, since it uses less digits than its factorization.

21204499816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2650562483 (or 2650562479 counting only the distinct ones).

The product of its (nonzero) digits is 248832, while the sum is 46.

The spelling of 21204499816 in words is "twenty-one billion, two hundred four million, four hundred ninety-nine thousand, eight hundred sixteen".