64644640 has 24 divisors (see below), whose sum is σ = 152723340. Its totient is φ = 25857792.

The previous prime is 64644637. The next prime is 64644649. The reversal of 64644640 is 4644646.

It can be written as a sum of positive squares in 2 ways, for example, as 57093136 + 7551504 = 7556^2 + 2748^2 .

It is a Smith number, since the sum of its digits (34) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 64644596 and 64644605.

It is not an unprimeable number, because it can be changed into a prime (64644649) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 201855 + ... + 202174.

Almost surely, 2^64644640 is an apocalyptic number.

It is an amenable number.

64644640 is an abundant number, since it is smaller than the sum of its proper divisors (88078700).

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

64644640 is a wasteful number, since it uses less digits than its factorization.

64644640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404044 (or 404036 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 34.

The square root of 64644640 is about 8040.1890525037. The cubic root of 64644640 is about 401.3385159416.

The spelling of 64644640 in words is "sixty-four million, six hundred forty-four thousand, six hundred forty".