640533631 has 2 divisors, whose sum is σ = 640533632. Its totient is φ = 640533630.

The previous prime is 640533629. The next prime is 640533661. The reversal of 640533631 is 136335046.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 640533631 - 2¹ = 640533629 is a prime.

It is a super-2 number, since 2×640533631² = 820566664884088322, which contains 22 as substring.

Together with 640533629, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 640533593 and 640533602.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640533661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320266815 + 320266816.

It is an arithmetic number, because the mean of its divisors is an integer number (320266816).

Almost surely, 2^640533631 is an apocalyptic number.

640533631 is a deficient number, since it is larger than the sum of its proper divisors (1).

640533631 is an equidigital number, since it uses as much as digits as its factorization.

640533631 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 19440, while the sum is 31.

The square root of 640533631 is about 25308.7658924729. The cubic root of 640533631 is about 862.0133247115.

Adding to 640533631 its reverse (136335046), we get a palindrome (776868677).

The spelling of 640533631 in words is "six hundred forty million, five hundred thirty-three thousand, six hundred thirty-one".