640042561 has 8 divisors (see below), whose sum is σ = 661564800. Its totient is φ = 618876240.

The previous prime is 640042553. The next prime is 640042567. The reversal of 640042561 is 165240046.

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

It is a cyclic number.

It is not a de Polignac number, because 640042561 - 2³ = 640042553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640042567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 85321 + ... + 92518.

It is an arithmetic number, because the mean of its divisors is an integer number (82695600).

Almost surely, 2^640042561 is an apocalyptic number.

640042561 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

640042561 is a deficient number, since it is larger than the sum of its proper divisors (21522239).

640042561 is a wasteful number, since it uses less digits than its factorization.

640042561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177959.

The product of its (nonzero) digits is 5760, while the sum is 28.

The square root of 640042561 is about 25299.0624529843. The cubic root of 640042561 is about 861.7929786924.

The spelling of 640042561 in words is "six hundred forty million, forty-two thousand, five hundred sixty-one".