21206566404 has 36 divisors (see below), whose sum is σ = 54136243980. Its totient is φ = 6998865600.

The previous prime is 21206566399. The next prime is 21206566417. The reversal of 21206566404 is 40466560212.

21206566404 is a `hidden beast` number, since 2 + 1 + 2 + 0 + 6 + 5 + 6 + 640 + 4 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 17635308804 + 3571257600 = 132798^2 + 59760^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×21206566404² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2912559 + ... + 2919830.

It is an arithmetic number, because the mean of its divisors is an integer number (1503784555).

Almost surely, 2^21206566404 is an apocalyptic number.

It is an amenable number.

21206566404 is an abundant number, since it is smaller than the sum of its proper divisors (32929677576).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21206566404 is a wasteful number, since it uses less digits than its factorization.

21206566404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5832500 (or 5832495 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

The spelling of 21206566404 in words is "twenty-one billion, two hundred six million, five hundred sixty-six thousand, four hundred four".