640344947 has 6 divisors (see below), whose sum is σ = 703850364. Its totient is φ = 582131660.

The previous prime is 640344937. The next prime is 640344979. The reversal of 640344947 is 749443046.

It is a happy number.

It is not a de Polignac number, because 640344947 - 2⁶ = 640344883 is a prime.

It is a super-2 number, since 2×640344947² = 820083302296865618, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640344907) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2645933 + ... + 2646174.

It is an arithmetic number, because the mean of its divisors is an integer number (117308394).

Almost surely, 2^640344947 is an apocalyptic number.

640344947 is a deficient number, since it is larger than the sum of its proper divisors (63505417).

640344947 is a wasteful number, since it uses less digits than its factorization.

640344947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5292129 (or 5292118 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 41.

The square root of 640344947 is about 25305.0379766560. The cubic root of 640344947 is about 861.9286744098.

The spelling of 640344947 in words is "six hundred forty million, three hundred forty-four thousand, nine hundred forty-seven".