646663680 has 480 divisors, whose sum is σ = 2573835264. Its totient is φ = 148635648.

The previous prime is 646663673. The next prime is 646663681. The reversal of 646663680 is 86366646.

It is a tau number, because it is divible by the number of its divisors (480).

It is a super-2 number, since 2×646663680² = 836347830062284800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646663681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 5091777 + ... + 5091903.

Almost surely, 2^646663680 is an apocalyptic number.

646663680 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 646663680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1286917632).

646663680 is an abundant number, since it is smaller than the sum of its proper divisors (1927171584).

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

646663680 is a wasteful number, since it uses less digits than its factorization.

646663680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186 (or 167 counting only the distinct ones).

The product of its (nonzero) digits is 746496, while the sum is 45.

The square root of 646663680 is about 25429.5827728258. The cubic root of 646663680 is about 864.7544849898.

The spelling of 646663680 in words is "six hundred forty-six million, six hundred sixty-three thousand, six hundred eighty".