640400591 has 24 divisors (see below), whose sum is σ = 720516720. Its totient is φ = 568092672.

The previous prime is 640400549. The next prime is 640400599. The reversal of 640400591 is 195004046.

It is not a de Polignac number, because 640400591 - 2¹⁰ = 640399567 is a prime.

It is a super-2 number, since 2×640400591² = 820225833906298562, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640400599) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 359495 + ... + 361271.

It is an arithmetic number, because the mean of its divisors is an integer number (30021530).

Almost surely, 2^640400591 is an apocalyptic number.

640400591 is a deficient number, since it is larger than the sum of its proper divisors (80116129).

640400591 is a wasteful number, since it uses less digits than its factorization.

640400591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1883 (or 1866 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 640400591 is about 25306.1374176305. The cubic root of 640400591 is about 861.9536400007.

The spelling of 640400591 in words is "six hundred forty million, four hundred thousand, five hundred ninety-one".