640431555 has 16 divisors (see below), whose sum is σ = 1038729120. Its totient is φ = 336883968.

The previous prime is 640431523. The next prime is 640431593. The reversal of 640431555 is 555134046.

It is not a de Polignac number, because 640431555 - 2⁵ = 640431523 is a prime.

It is a super-3 number, since 3×640431555³ (a number of 27 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 291340 + ... + 293529.

It is an arithmetic number, because the mean of its divisors is an integer number (64920570).

Almost surely, 2^640431555 is an apocalyptic number.

640431555 is a deficient number, since it is larger than the sum of its proper divisors (398297565).

640431555 is a wasteful number, since it uses less digits than its factorization.

640431555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 584950.

The product of its (nonzero) digits is 36000, while the sum is 33.

The square root of 640431555 is about 25306.7491985834. The cubic root of 640431555 is about 861.9675318796.

The spelling of 640431555 in words is "six hundred forty million, four hundred thirty-one thousand, five hundred fifty-five".