640471 has 8 divisors (see below), whose sum is σ = 726320. Its totient is φ = 559872.

The previous prime is 640463. The next prime is 640477. The reversal of 640471 is 174046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 8-Lehmer number, since φ(640471) divides (640471-1)⁸.

It is a cyclic number.

It is not a de Polignac number, because 640471 - 2³ = 640463 is a prime.

It is a super-3 number, since 3×640471³ = 788169572517621333, which contains 333 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 (640477) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1050 + ... + 1543.

It is an arithmetic number, because the mean of its divisors is an integer number (90790).

2⁶⁴⁰⁴⁷¹ is an apocalyptic number.

640471 is a deficient number, since it is larger than the sum of its proper divisors (85849).

640471 is a wasteful number, since it uses less digits than its factorization.

640471 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2625.

The product of its (nonzero) digits is 672, while the sum is 22.

The square root of 640471 is about 800.2943208595. The cubic root of 640471 is about 86.1985228078.

It can be divided in two parts, 640 and 471, that added together give a palindrome (1111).

The spelling of 640471 in words is "six hundred forty thousand, four hundred seventy-one".