640420755 has 32 divisors (see below), whose sum is σ = 1104741120. Its totient is φ = 314928000.

The previous prime is 640420733. The next prime is 640420757. The reversal of 640420755 is 557024046.

It is not a de Polignac number, because 640420755 - 2⁶ = 640420691 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640420757) 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 31 ways as a sum of consecutive naturals, for example, 283380 + ... + 285630.

It is an arithmetic number, because the mean of its divisors is an integer number (34523160).

Almost surely, 2^640420755 is an apocalyptic number.

640420755 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

640420755 is a deficient number, since it is larger than the sum of its proper divisors (464320365).

640420755 is a wasteful number, since it uses less digits than its factorization.

640420755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3731.

The product of its (nonzero) digits is 33600, while the sum is 33.

The square root of 640420755 is about 25306.5358158718. The cubic root of 640420755 is about 861.9626865522.

The spelling of 640420755 in words is "six hundred forty million, four hundred twenty thousand, seven hundred fifty-five".