20645550666 has 48 divisors (see below), whose sum is σ = 48213199944. Its totient is φ = 6347169792.

The previous prime is 20645550661. The next prime is 20645550683. The reversal of 20645550666 is 66605554602.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 10894975641 + 9750575025 = 104379^2 + 98745^2 .

It is not an unprimeable number, because it can be changed into a prime (20645550661) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 248530 + ... + 321026.

Almost surely, 2^20645550666 is an apocalyptic number.

20645550666 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

20645550666 is an abundant number, since it is smaller than the sum of its proper divisors (27567649278).

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

20645550666 is a wasteful number, since it uses less digits than its factorization.

20645550666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73735 (or 73732 counting only the distinct ones).

The product of its (nonzero) digits is 1296000, while the sum is 45.

The spelling of 20645550666 in words is "twenty billion, six hundred forty-five million, five hundred fifty thousand, six hundred sixty-six".