21664435536720 has 200 divisors, whose sum is σ = 75440261799936. Its totient is φ = 5762098121472.

The previous prime is 21664435536713. The next prime is 21664435536727. The reversal of 21664435536720 is 2763553446612.

21664435536720 is a `hidden beast` number, since 2 + 1 + 6 + 6 + 4 + 4 + 3 + 553 + 67 + 20 = 666.

It is an interprime number because it is at equal distance from previous prime (21664435536713) and next prime (21664435536727).

It is a super-3 number, since 3×21664435536720³ (a number of 41 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664435536727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1882752 + ... + 6846431.

Almost surely, 2^{21664435536720} is an apocalyptic number.

21664435536720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21664435536720 is an abundant number, since it is smaller than the sum of its proper divisors (53775826263216).

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

21664435536720 is a wasteful number, since it uses less digits than its factorization.

21664435536720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8729591 (or 8729576 counting only the distinct ones).

The product of its (nonzero) digits is 21772800, while the sum is 54.

The spelling of 21664435536720 in words is "twenty-one trillion, six hundred sixty-four billion, four hundred thirty-five million, five hundred thirty-six thousand, seven hundred twenty".