64821640 has 96 divisors (see below), whose sum is σ = 162328320. Its totient is φ = 23272704.

The previous prime is 64821623. The next prime is 64821643. The reversal of 64821640 is 4612846.

64821640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (64821643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 290569 + ... + 290791.

It is an arithmetic number, because the mean of its divisors is an integer number (1690920).

Almost surely, 2^64821640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 64821640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (81164160).

64821640 is an abundant number, since it is smaller than the sum of its proper divisors (97506680).

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

64821640 is a wasteful number, since it uses less digits than its factorization.

64821640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 303 (or 286 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 31.

The square root of 64821640 is about 8051.1887321066. The cubic root of 64821640 is about 401.7044765825.

The spelling of 64821640 in words is "sixty-four million, eight hundred twenty-one thousand, six hundred forty".