640041691 has 4 divisors (see below), whose sum is σ = 646255792. Its totient is φ = 633827592.

The previous prime is 640041679. The next prime is 640041739. The reversal of 640041691 is 196140046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 196140046 = 2 ⋅98070023.

It is a cyclic number.

It is not a de Polignac number, because 640041691 - 2⁵ = 640041659 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640041601) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3106896 + ... + 3107101.

It is an arithmetic number, because the mean of its divisors is an integer number (161563948).

Almost surely, 2^640041691 is an apocalyptic number.

640041691 is a deficient number, since it is larger than the sum of its proper divisors (6214101).

640041691 is a wasteful number, since it uses less digits than its factorization.

640041691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6214100.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 640041691 is about 25299.0452586654. The cubic root of 640041691 is about 861.7925882182.

The spelling of 640041691 in words is "six hundred forty million, forty-one thousand, six hundred ninety-one".