21566420069 has 8 divisors (see below), whose sum is σ = 21598599000. Its totient is φ = 21534262272.

The previous prime is 21566420063. The next prime is 21566420077. The reversal of 21566420069 is 96002466512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 210105025 + 21356315044 = 14495^2 + 146138^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21566420069 - 2²⁰ = 21565371493 is a prime.

It is a super-2 number, since 2×21566420069² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21566420063) 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 7 ways as a sum of consecutive naturals, for example, 4390787 + ... + 4395695.

It is an arithmetic number, because the mean of its divisors is an integer number (2699824875).

Almost surely, 2^21566420069 is an apocalyptic number.

It is an amenable number.

21566420069 is a deficient number, since it is larger than the sum of its proper divisors (32178931).

21566420069 is an equidigital number, since it uses as much as digits as its factorization.

21566420069 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10567.

The product of its (nonzero) digits is 155520, while the sum is 41.

The spelling of 21566420069 in words is "twenty-one billion, five hundred sixty-six million, four hundred twenty thousand, sixty-nine".