21646646825 has 12 divisors (see below), whose sum is σ = 26843847360. Its totient is φ = 17316023760.

The previous prime is 21646646809. The next prime is 21646646867. The reversal of 21646646825 is 52864664612.

It is not a de Polignac number, because 21646646825 - 2⁴ = 21646646809 is a prime.

It is a Curzon number.

It is an unprimeable number.

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 11 ways as a sum of consecutive naturals, for example, 450092 + ... + 495858.

It is an arithmetic number, because the mean of its divisors is an integer number (2236987280).

Almost surely, 2^21646646825 is an apocalyptic number.

21646646825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21646646825 is a deficient number, since it is larger than the sum of its proper divisors (5197200535).

21646646825 is a wasteful number, since it uses less digits than its factorization.

21646646825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64696 (or 64691 counting only the distinct ones).

The product of its digits is 3317760, while the sum is 50.

The spelling of 21646646825 in words is "twenty-one billion, six hundred forty-six million, six hundred forty-six thousand, eight hundred twenty-five".