640392479 has 4 divisors (see below), whose sum is σ = 642206976. Its totient is φ = 638577984.

The previous prime is 640392461. The next prime is 640392497. The reversal of 640392479 is 974293046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 974293046 = 2 ⋅487146523.

It is an interprime number because it is at equal distance from previous prime (640392461) and next prime (640392497).

It is a cyclic number.

It is not a de Polignac number, because 640392479 - 2¹² = 640388383 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640392409) 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 in 3 ways as a sum of consecutive naturals, for example, 906719 + ... + 907424.

It is an arithmetic number, because the mean of its divisors is an integer number (160551744).

Almost surely, 2^640392479 is an apocalyptic number.

640392479 is a deficient number, since it is larger than the sum of its proper divisors (1814497).

640392479 is a wasteful number, since it uses less digits than its factorization.

640392479 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1814496.

The product of its (nonzero) digits is 326592, while the sum is 44.

The square root of 640392479 is about 25305.9771397984. The cubic root of 640392479 is about 861.9500005093.

The spelling of 640392479 in words is "six hundred forty million, three hundred ninety-two thousand, four hundred seventy-nine".