640393635 has 32 divisors (see below), whose sum is σ = 1175910912. Its totient is φ = 291525120.

The previous prime is 640393603. The next prime is 640393657. The reversal of 640393635 is 536393046.

It is a Cunningham number, because it is equal to 25306²-1.

It is not a de Polignac number, because 640393635 - 2⁵ = 640393603 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a junction number, because it is equal to n+sod(n) for n = 640393593 and 640393602.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12652 + ... + 37958.

It is an arithmetic number, because the mean of its divisors is an integer number (36747216).

Almost surely, 2^640393635 is an apocalyptic number.

640393635 is a deficient number, since it is larger than the sum of its proper divisors (535517277).

640393635 is a wasteful number, since it uses less digits than its factorization.

640393635 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25563.

The product of its (nonzero) digits is 174960, while the sum is 39.

The square root of 640393635 is about 25305.9999802418. Note that the first 4 decimals coincide. The cubic root of 640393635 is about 861.9505191566.

The spelling of 640393635 in words is "six hundred forty million, three hundred ninety-three thousand, six hundred thirty-five".