640424720 has 40 divisors (see below), whose sum is σ = 1603527576. Its totient is φ = 236464128.

The previous prime is 640424699. The next prime is 640424737. The reversal of 640424720 is 27424046.

It can be written as a sum of positive squares in 4 ways, for example, as 122589184 + 517835536 = 11072^2 + 22756^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 306857 + ... + 308936.

Almost surely, 2^640424720 is an apocalyptic number.

It is an amenable number.

640424720 is an abundant number, since it is smaller than the sum of its proper divisors (963102856).

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

640424720 is a wasteful number, since it uses less digits than its factorization.

640424720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 615819 (or 615813 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 29.

The square root of 640424720 is about 25306.6141551967. The cubic root of 640424720 is about 861.9644654218.

Adding to 640424720 its reverse (27424046), we get a palindrome (667848766).

The spelling of 640424720 in words is "six hundred forty million, four hundred twenty-four thousand, seven hundred twenty".