640720235 has 16 divisors (see below), whose sum is σ = 783751680. Its totient is φ = 502692960.

The previous prime is 640720217. The next prime is 640720273. The reversal of 640720235 is 532027046.

640720235 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a de Polignac number, because none of the positive numbers 2^k-640720235 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 640720198 and 640720207.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 134240 + ... + 138930.

It is an arithmetic number, because the mean of its divisors is an integer number (48984480).

Almost surely, 2^640720235 is an apocalyptic number.

640720235 is a deficient number, since it is larger than the sum of its proper divisors (143031445).

640720235 is a wasteful number, since it uses less digits than its factorization.

640720235 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5218.

The product of its (nonzero) digits is 10080, while the sum is 29.

The square root of 640720235 is about 25312.4521727943. The cubic root of 640720235 is about 862.0970255035.

The spelling of 640720235 in words is "six hundred forty million, seven hundred twenty thousand, two hundred thirty-five".