640138951 has 2 divisors, whose sum is σ = 640138952. Its totient is φ = 640138950.

The previous prime is 640138943. The next prime is 640138969. The reversal of 640138951 is 159831046.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 640138951 - 2³ = 640138943 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 640138951.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640138931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320069475 + 320069476.

It is an arithmetic number, because the mean of its divisors is an integer number (320069476).

Almost surely, 2^640138951 is an apocalyptic number.

640138951 is a deficient number, since it is larger than the sum of its proper divisors (1).

640138951 is an equidigital number, since it uses as much as digits as its factorization.

640138951 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 640138951 is about 25300.9673925722. The cubic root of 640138951 is about 861.8362383445.

Adding to 640138951 its reverse (159831046), we get a palindrome (799969997).

The spelling of 640138951 in words is "six hundred forty million, one hundred thirty-eight thousand, nine hundred fifty-one".