640743938 has 4 divisors (see below), whose sum is σ = 961115910. Its totient is φ = 320371968.

The previous prime is 640743937. The next prime is 640743947. The reversal of 640743938 is 839347046.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 549292969 + 91450969 = 23437^2 + 9563^2 .

It is not an unprimeable number, because it can be changed into a prime (640743937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160185983 + ... + 160185986.

Almost surely, 2^640743938 is an apocalyptic number.

640743938 is a deficient number, since it is larger than the sum of its proper divisors (320371972).

640743938 is a wasteful number, since it uses less digits than its factorization.

640743938 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320371971.

The product of its (nonzero) digits is 435456, while the sum is 44.

The square root of 640743938 is about 25312.9203767562. The cubic root of 640743938 is about 862.1076562659.

The spelling of 640743938 in words is "six hundred forty million, seven hundred forty-three thousand, nine hundred thirty-eight".