640309879 has 32 divisors (see below), whose sum is σ = 776355840. Its totient is φ = 521203200.

The previous prime is 640309843. The next prime is 640309883. The reversal of 640309879 is 978903046.

It is a cyclic number.

It is not a de Polignac number, because 640309879 - 2¹¹ = 640307831 is a prime.

It is a super-2 number, since 2×640309879² = 819993482289989282, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640309819) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 384202 + ... + 385864.

It is an arithmetic number, because the mean of its divisors is an integer number (24261120).

Almost surely, 2^640309879 is an apocalyptic number.

640309879 is a deficient number, since it is larger than the sum of its proper divisors (136045961).

640309879 is a wasteful number, since it uses less digits than its factorization.

640309879 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1791.

The product of its (nonzero) digits is 326592, while the sum is 46.

The square root of 640309879 is about 25304.3450616688. The cubic root of 640309879 is about 861.9129398349.

The spelling of 640309879 in words is "six hundred forty million, three hundred nine thousand, eight hundred seventy-nine".